Injected LRU capabilities that simply:

* ensures that when an item is added, if the number of unexpired items
>= maximum number of items specified, the oldest (based on ACCESS) is
expired
* when an item is "gotten", or "set", the access time is updated

The existing janitor system is unchanged, and used to actually delete
the items.

The only change from a consumer standpoint, is one addition parameter at
the end of a "New" call, that specifies the maximum number of items to
allow, or 0, if you want to disable the LRU at all.

CONTRIBUTORS

@@ -6,3 +6,4 @@ code was contributed.)
 Dustin Sallings <dustin@spy.net>
 Jason Mooberry <jasonmoo@me.com>
 Sergey Shepelev <temotor@gmail.com>
+Matthew Keller	<m@cognusion.com>

cache.go

@@ -13,6 +13,8 @@ import (
 type Item struct {
 	Object     interface{}
 	Expiration *time.Time
+	Ctime      *time.Time
+	Atime      *time.Time
 }
 
 // Returns true if the item has expired.
@@ -23,6 +25,21 @@ func (item *Item) Expired() bool {
 	return item.Expiration.Before(time.Now())
 }
 
+// Return the Atime
+func (item *Item) LastAccessed() *time.Time {
+	return item.Atime
+}
+
+func (item *Item) Accessed() {
+	now := time.Now()
+	item.Atime = &now
+}
+
+// Return the Ctime
+func (item *Item) Created() *time.Time {
+	return item.Ctime
+}
+
 const (
 	// For use with functions that take an expiration time.
 	NoExpiration time.Duration = -1
@@ -42,6 +59,7 @@ type cache struct {
 	defaultExpiration time.Duration
 	items             map[string]*Item
 	janitor           *janitor
+	maxItems          int
 }
 
 // Add an item to the cache, replacing any existing item. If the duration is 0
@@ -57,16 +75,40 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
 
 func (c *cache) set(k string, x interface{}, d time.Duration) {
 	var e *time.Time
+	t := time.Now()
+	at := &t
+	ct := &t
+	
 	if d == DefaultExpiration {
 		d = c.defaultExpiration
 	}
 	if d > 0 {
-		t := time.Now().Add(d)
+		t = time.Now().Add(d)
 		e = &t
 	}
-	c.items[k] = &Item{
-		Object:     x,
-		Expiration: e,
+	
+	if c.maxItems > 0 {
+		// We don't want to hit the expiration if we're updating.
+		_, found := c.get(k)
+		if ! found {
+			// Create, means maybe expire
+			c.ExpireLRU() 
+		} else {
+			// Update, means don't expire, or change the Ctime
+			ct = c.items[k].Created() 	
+		}
+		c.items[k] = &Item{
+			Object:     x,
+			Expiration: e,
+			Ctime:      ct,
+			Atime:      at,
+		}
+	} else {
+		// Not using maxItems
+		c.items[k] = &Item{
+			Object:     x,
+			Expiration: e,
+		}
 	}
 }
 
@@ -112,6 +154,9 @@ func (c *cache) get(k string) (interface{}, bool) {
 	if !found || item.Expired() {
 		return nil, false
 	}
+	
+	if c.maxItems > 0 { item.Accessed() }
+	
 	return item.Object, true
 }
 
@@ -127,6 +172,9 @@ func (c *cache) Increment(k string, n int64) error {
 		c.Unlock()
 		return fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	switch v.Object.(type) {
 	case int:
 		v.Object = v.Object.(int) + int(n)
@@ -174,6 +222,9 @@ func (c *cache) IncrementFloat(k string, n float64) error {
 		c.Unlock()
 		return fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	switch v.Object.(type) {
 	case float32:
 		v.Object = v.Object.(float32) + float32(n)
@@ -197,6 +248,9 @@ func (c *cache) IncrementInt(k string, n int) (int, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int)
 	if !ok {
 		c.Unlock()
@@ -218,6 +272,9 @@ func (c *cache) IncrementInt8(k string, n int8) (int8, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int8)
 	if !ok {
 		c.Unlock()
@@ -239,6 +296,9 @@ func (c *cache) IncrementInt16(k string, n int16) (int16, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int16)
 	if !ok {
 		c.Unlock()
@@ -260,6 +320,9 @@ func (c *cache) IncrementInt32(k string, n int32) (int32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int32)
 	if !ok {
 		c.Unlock()
@@ -281,6 +344,9 @@ func (c *cache) IncrementInt64(k string, n int64) (int64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int64)
 	if !ok {
 		c.Unlock()
@@ -302,6 +368,9 @@ func (c *cache) IncrementUint(k string, n uint) (uint, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint)
 	if !ok {
 		c.Unlock()
@@ -323,6 +392,9 @@ func (c *cache) IncrementUintptr(k string, n uintptr) (uintptr, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uintptr)
 	if !ok {
 		c.Unlock()
@@ -344,6 +416,9 @@ func (c *cache) IncrementUint8(k string, n uint8) (uint8, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint8)
 	if !ok {
 		c.Unlock()
@@ -365,6 +440,9 @@ func (c *cache) IncrementUint16(k string, n uint16) (uint16, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+
+	if c.maxItems > 0 { v.Accessed() }
+
 	rv, ok := v.Object.(uint16)
 	if !ok {
 		c.Unlock()
@@ -386,6 +464,9 @@ func (c *cache) IncrementUint32(k string, n uint32) (uint32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint32)
 	if !ok {
 		c.Unlock()
@@ -407,6 +488,9 @@ func (c *cache) IncrementUint64(k string, n uint64) (uint64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint64)
 	if !ok {
 		c.Unlock()
@@ -428,6 +512,9 @@ func (c *cache) IncrementFloat32(k string, n float32) (float32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(float32)
 	if !ok {
 		c.Unlock()
@@ -449,6 +536,9 @@ func (c *cache) IncrementFloat64(k string, n float64) (float64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(float64)
 	if !ok {
 		c.Unlock()
@@ -474,6 +564,9 @@ func (c *cache) Decrement(k string, n int64) error {
 		c.Unlock()
 		return fmt.Errorf("Item not found")
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	switch v.Object.(type) {
 	case int:
 		v.Object = v.Object.(int) - int(n)
@@ -521,6 +614,9 @@ func (c *cache) DecrementFloat(k string, n float64) error {
 		c.Unlock()
 		return fmt.Errorf("Item %s not found", k)
 	}
+
+	if c.maxItems > 0 { v.Accessed() }
+	
 	switch v.Object.(type) {
 	case float32:
 		v.Object = v.Object.(float32) - float32(n)
@@ -544,6 +640,9 @@ func (c *cache) DecrementInt(k string, n int) (int, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int)
 	if !ok {
 		c.Unlock()
@@ -565,6 +664,9 @@ func (c *cache) DecrementInt8(k string, n int8) (int8, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int8)
 	if !ok {
 		c.Unlock()
@@ -586,6 +688,9 @@ func (c *cache) DecrementInt16(k string, n int16) (int16, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int16)
 	if !ok {
 		c.Unlock()
@@ -607,6 +712,9 @@ func (c *cache) DecrementInt32(k string, n int32) (int32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int32)
 	if !ok {
 		c.Unlock()
@@ -628,6 +736,9 @@ func (c *cache) DecrementInt64(k string, n int64) (int64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(int64)
 	if !ok {
 		c.Unlock()
@@ -649,6 +760,9 @@ func (c *cache) DecrementUint(k string, n uint) (uint, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint)
 	if !ok {
 		c.Unlock()
@@ -670,6 +784,9 @@ func (c *cache) DecrementUintptr(k string, n uintptr) (uintptr, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uintptr)
 	if !ok {
 		c.Unlock()
@@ -691,6 +808,9 @@ func (c *cache) DecrementUint8(k string, n uint8) (uint8, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint8)
 	if !ok {
 		c.Unlock()
@@ -712,6 +832,9 @@ func (c *cache) DecrementUint16(k string, n uint16) (uint16, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint16)
 	if !ok {
 		c.Unlock()
@@ -733,6 +856,9 @@ func (c *cache) DecrementUint32(k string, n uint32) (uint32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint32)
 	if !ok {
 		c.Unlock()
@@ -754,6 +880,9 @@ func (c *cache) DecrementUint64(k string, n uint64) (uint64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(uint64)
 	if !ok {
 		c.Unlock()
@@ -775,6 +904,9 @@ func (c *cache) DecrementFloat32(k string, n float32) (float32, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(float32)
 	if !ok {
 		c.Unlock()
@@ -796,6 +928,9 @@ func (c *cache) DecrementFloat64(k string, n float64) (float64, error) {
 		c.Unlock()
 		return 0, fmt.Errorf("Item %s not found", k)
 	}
+	
+	if c.maxItems > 0 { v.Accessed() }
+	
 	rv, ok := v.Object.(float64)
 	if !ok {
 		c.Unlock()
@@ -927,6 +1062,19 @@ func (c *cache) ItemCount() int {
 	return n
 }
 
+// Returns the number of items in the cache *that have not expired*
+func (c *cache) itemCount() int {
+	n := 0
+	now := time.Now()
+	
+	for _, v := range c.items {
+		if v.Expiration == nil || ! v.Expiration.Before(now) {
+			n++
+		}
+	}
+	return n
+}
+
 // Delete all items from the cache.
 func (c *cache) Flush() {
 	c.Lock()
@@ -934,6 +1082,50 @@ func (c *cache) Flush() {
 	c.Unlock()
 }
 
+// Find oldest N items, and Expire them.
+// Returns the number "expired".
+// BIG HAIRY ALERT: This function assumes it is called
+// from inside a c.Lock() .. c.Unlock() block. 
+func (c *cache) ExpireLRU() {
+
+	// We need the number of UNexpired Items
+	itemCount := c.itemCount()
+
+	if itemCount >= c.maxItems {
+	
+		// Cache the current time.
+		// We do this "early" so that when we set an Expiration,
+		// it is definitely "do" when the janitor ticks
+		notw := time.Now()
+
+		var lastTime int64 = 0
+		var lastName string = ""
+
+		for k, v := range c.items {
+			if v.Expired() == false {
+				// unexpired item
+				
+				atime := v.LastAccessed().UnixNano()
+				if lastTime == 0 {
+					// We need to expire something, so let's start with the first item
+					lastTime = atime
+					lastName = k
+				} else if atime < lastTime {
+					// We found a least-recently-used item
+					lastTime = atime
+					lastName = k
+				}
+			}
+		}
+		
+		if lastTime > 0 {
+			// We expire the item, but making it look .Expired(), 
+			// so the janitor will clean it up for us
+			c.items[lastName].Expiration = &notw
+		}
+	}
+}
+
 type janitor struct {
 	Interval time.Duration
 	stop     chan bool
@@ -964,19 +1156,20 @@ func runJanitor(c *cache, ci time.Duration) {
 	go j.Run(c)
 }
 
-func newCache(de time.Duration, m map[string]*Item) *cache {
+func newCache(de time.Duration, m map[string]*Item, mi int) *cache {
 	if de == 0 {
 		de = -1
 	}
 	c := &cache{
 		defaultExpiration: de,
+		maxItems:          mi,
 		items:             m,
 	}
 	return c
 }
 
-func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]*Item) *Cache {
-	c := newCache(de, m)
+func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]*Item, mi int) *Cache {
+	c := newCache(de, m, mi)
 	// This trick ensures that the janitor goroutine (which--granted it
 	// was enabled--is running DeleteExpired on c forever) does not keep
 	// the returned C object from being garbage collected. When it is
@@ -995,9 +1188,9 @@ func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]*Item)
 // the items in the cache never expire (by default), and must be deleted
 // manually. If the cleanup interval is less than one, expired items are not
 // deleted from the cache before calling c.DeleteExpired().
-func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
+func New(defaultExpiration, cleanupInterval time.Duration,  maxItems int) *Cache {
 	items := make(map[string]*Item)
-	return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
+	return newCacheWithJanitor(defaultExpiration, cleanupInterval, items, maxItems)
 }
 
 // Return a new cache with a given default expiration duration and cleanup
@@ -1021,6 +1214,6 @@ func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
 // gob.Register() the individual types stored in the cache before encoding a
 // map retrieved with c.Items(), and to register those same types before
 // decoding a blob containing an items map.
-func NewFrom(defaultExpiration, cleanupInterval time.Duration, items map[string]*Item) *Cache {
-	return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
+func NewFrom(defaultExpiration, cleanupInterval time.Duration, items map[string]*Item, maxItems int) *Cache {
+	return newCacheWithJanitor(defaultExpiration, cleanupInterval, items, maxItems)
 }

cache_test.go

@@ -16,7 +16,7 @@ type TestStruct struct {
 }
 
 func TestCache(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 
 	a, found := tc.Get("a")
 	if found || a != nil {
@@ -71,7 +71,7 @@ func TestCache(t *testing.T) {
 func TestCacheTimes(t *testing.T) {
 	var found bool
 
-	tc := New(50*time.Millisecond, 1*time.Millisecond)
+	tc := New(50*time.Millisecond, 1*time.Millisecond, 0)
 	tc.Set("a", 1, DefaultExpiration)
 	tc.Set("b", 2, NoExpiration)
 	tc.Set("c", 3, 20*time.Millisecond)
@@ -117,7 +117,7 @@ func TestNewFrom(t *testing.T) {
 			Expiration: nil,
 		},
 	}
-	tc := NewFrom(DefaultExpiration, 0, m)
+	tc := NewFrom(DefaultExpiration, 0, m, 0)
 	a, found := tc.Get("a")
 	if !found {
 		t.Fatal("Did not find a")
@@ -135,7 +135,7 @@ func TestNewFrom(t *testing.T) {
 }
 
 func TestStorePointerToStruct(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", &TestStruct{Num: 1}, DefaultExpiration)
 	x, found := tc.Get("foo")
 	if !found {
@@ -155,7 +155,7 @@ func TestStorePointerToStruct(t *testing.T) {
 }
 
 func TestIncrementWithInt(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint", 1, DefaultExpiration)
 	err := tc.Increment("tint", 2)
 	if err != nil {
@@ -171,7 +171,7 @@ func TestIncrementWithInt(t *testing.T) {
 }
 
 func TestIncrementWithInt8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint8", int8(1), DefaultExpiration)
 	err := tc.Increment("tint8", 2)
 	if err != nil {
@@ -187,7 +187,7 @@ func TestIncrementWithInt8(t *testing.T) {
 }
 
 func TestIncrementWithInt16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint16", int16(1), DefaultExpiration)
 	err := tc.Increment("tint16", 2)
 	if err != nil {
@@ -203,7 +203,7 @@ func TestIncrementWithInt16(t *testing.T) {
 }
 
 func TestIncrementWithInt32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint32", int32(1), DefaultExpiration)
 	err := tc.Increment("tint32", 2)
 	if err != nil {
@@ -219,7 +219,7 @@ func TestIncrementWithInt32(t *testing.T) {
 }
 
 func TestIncrementWithInt64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint64", int64(1), DefaultExpiration)
 	err := tc.Increment("tint64", 2)
 	if err != nil {
@@ -235,7 +235,7 @@ func TestIncrementWithInt64(t *testing.T) {
 }
 
 func TestIncrementWithUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint", uint(1), DefaultExpiration)
 	err := tc.Increment("tuint", 2)
 	if err != nil {
@@ -251,7 +251,7 @@ func TestIncrementWithUint(t *testing.T) {
 }
 
 func TestIncrementWithUintptr(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuintptr", uintptr(1), DefaultExpiration)
 	err := tc.Increment("tuintptr", 2)
 	if err != nil {
@@ -268,7 +268,7 @@ func TestIncrementWithUintptr(t *testing.T) {
 }
 
 func TestIncrementWithUint8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint8", uint8(1), DefaultExpiration)
 	err := tc.Increment("tuint8", 2)
 	if err != nil {
@@ -284,7 +284,7 @@ func TestIncrementWithUint8(t *testing.T) {
 }
 
 func TestIncrementWithUint16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint16", uint16(1), DefaultExpiration)
 	err := tc.Increment("tuint16", 2)
 	if err != nil {
@@ -301,7 +301,7 @@ func TestIncrementWithUint16(t *testing.T) {
 }
 
 func TestIncrementWithUint32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint32", uint32(1), DefaultExpiration)
 	err := tc.Increment("tuint32", 2)
 	if err != nil {
@@ -317,7 +317,7 @@ func TestIncrementWithUint32(t *testing.T) {
 }
 
 func TestIncrementWithUint64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint64", uint64(1), DefaultExpiration)
 	err := tc.Increment("tuint64", 2)
 	if err != nil {
@@ -334,7 +334,7 @@ func TestIncrementWithUint64(t *testing.T) {
 }
 
 func TestIncrementWithFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(1.5), DefaultExpiration)
 	err := tc.Increment("float32", 2)
 	if err != nil {
@@ -350,7 +350,7 @@ func TestIncrementWithFloat32(t *testing.T) {
 }
 
 func TestIncrementWithFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(1.5), DefaultExpiration)
 	err := tc.Increment("float64", 2)
 	if err != nil {
@@ -366,7 +366,7 @@ func TestIncrementWithFloat64(t *testing.T) {
 }
 
 func TestIncrementFloatWithFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(1.5), DefaultExpiration)
 	err := tc.IncrementFloat("float32", 2)
 	if err != nil {
@@ -382,7 +382,7 @@ func TestIncrementFloatWithFloat32(t *testing.T) {
 }
 
 func TestIncrementFloatWithFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(1.5), DefaultExpiration)
 	err := tc.IncrementFloat("float64", 2)
 	if err != nil {
@@ -398,7 +398,7 @@ func TestIncrementFloatWithFloat64(t *testing.T) {
 }
 
 func TestDecrementWithInt(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int", int(5), DefaultExpiration)
 	err := tc.Decrement("int", 2)
 	if err != nil {
@@ -414,7 +414,7 @@ func TestDecrementWithInt(t *testing.T) {
 }
 
 func TestDecrementWithInt8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int8", int8(5), DefaultExpiration)
 	err := tc.Decrement("int8", 2)
 	if err != nil {
@@ -430,7 +430,7 @@ func TestDecrementWithInt8(t *testing.T) {
 }
 
 func TestDecrementWithInt16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int16", int16(5), DefaultExpiration)
 	err := tc.Decrement("int16", 2)
 	if err != nil {
@@ -446,7 +446,7 @@ func TestDecrementWithInt16(t *testing.T) {
 }
 
 func TestDecrementWithInt32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int32", int32(5), DefaultExpiration)
 	err := tc.Decrement("int32", 2)
 	if err != nil {
@@ -462,7 +462,7 @@ func TestDecrementWithInt32(t *testing.T) {
 }
 
 func TestDecrementWithInt64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int64", int64(5), DefaultExpiration)
 	err := tc.Decrement("int64", 2)
 	if err != nil {
@@ -478,7 +478,7 @@ func TestDecrementWithInt64(t *testing.T) {
 }
 
 func TestDecrementWithUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint", uint(5), DefaultExpiration)
 	err := tc.Decrement("uint", 2)
 	if err != nil {
@@ -494,7 +494,7 @@ func TestDecrementWithUint(t *testing.T) {
 }
 
 func TestDecrementWithUintptr(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uintptr", uintptr(5), DefaultExpiration)
 	err := tc.Decrement("uintptr", 2)
 	if err != nil {
@@ -510,7 +510,7 @@ func TestDecrementWithUintptr(t *testing.T) {
 }
 
 func TestDecrementWithUint8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint8", uint8(5), DefaultExpiration)
 	err := tc.Decrement("uint8", 2)
 	if err != nil {
@@ -526,7 +526,7 @@ func TestDecrementWithUint8(t *testing.T) {
 }
 
 func TestDecrementWithUint16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint16", uint16(5), DefaultExpiration)
 	err := tc.Decrement("uint16", 2)
 	if err != nil {
@@ -542,7 +542,7 @@ func TestDecrementWithUint16(t *testing.T) {
 }
 
 func TestDecrementWithUint32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint32", uint32(5), DefaultExpiration)
 	err := tc.Decrement("uint32", 2)
 	if err != nil {
@@ -558,7 +558,7 @@ func TestDecrementWithUint32(t *testing.T) {
 }
 
 func TestDecrementWithUint64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint64", uint64(5), DefaultExpiration)
 	err := tc.Decrement("uint64", 2)
 	if err != nil {
@@ -574,7 +574,7 @@ func TestDecrementWithUint64(t *testing.T) {
 }
 
 func TestDecrementWithFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(5.5), DefaultExpiration)
 	err := tc.Decrement("float32", 2)
 	if err != nil {
@@ -590,7 +590,7 @@ func TestDecrementWithFloat32(t *testing.T) {
 }
 
 func TestDecrementWithFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(5.5), DefaultExpiration)
 	err := tc.Decrement("float64", 2)
 	if err != nil {
@@ -606,7 +606,7 @@ func TestDecrementWithFloat64(t *testing.T) {
 }
 
 func TestDecrementFloatWithFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(5.5), DefaultExpiration)
 	err := tc.DecrementFloat("float32", 2)
 	if err != nil {
@@ -622,7 +622,7 @@ func TestDecrementFloatWithFloat32(t *testing.T) {
 }
 
 func TestDecrementFloatWithFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(5.5), DefaultExpiration)
 	err := tc.DecrementFloat("float64", 2)
 	if err != nil {
@@ -638,7 +638,7 @@ func TestDecrementFloatWithFloat64(t *testing.T) {
 }
 
 func TestIncrementInt(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint", 1, DefaultExpiration)
 	n, err := tc.IncrementInt("tint", 2)
 	if err != nil {
@@ -657,7 +657,7 @@ func TestIncrementInt(t *testing.T) {
 }
 
 func TestIncrementInt8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint8", int8(1), DefaultExpiration)
 	n, err := tc.IncrementInt8("tint8", 2)
 	if err != nil {
@@ -676,7 +676,7 @@ func TestIncrementInt8(t *testing.T) {
 }
 
 func TestIncrementInt16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint16", int16(1), DefaultExpiration)
 	n, err := tc.IncrementInt16("tint16", 2)
 	if err != nil {
@@ -695,7 +695,7 @@ func TestIncrementInt16(t *testing.T) {
 }
 
 func TestIncrementInt32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint32", int32(1), DefaultExpiration)
 	n, err := tc.IncrementInt32("tint32", 2)
 	if err != nil {
@@ -714,7 +714,7 @@ func TestIncrementInt32(t *testing.T) {
 }
 
 func TestIncrementInt64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tint64", int64(1), DefaultExpiration)
 	n, err := tc.IncrementInt64("tint64", 2)
 	if err != nil {
@@ -733,7 +733,7 @@ func TestIncrementInt64(t *testing.T) {
 }
 
 func TestIncrementUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint", uint(1), DefaultExpiration)
 	n, err := tc.IncrementUint("tuint", 2)
 	if err != nil {
@@ -752,7 +752,7 @@ func TestIncrementUint(t *testing.T) {
 }
 
 func TestIncrementUintptr(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuintptr", uintptr(1), DefaultExpiration)
 	n, err := tc.IncrementUintptr("tuintptr", 2)
 	if err != nil {
@@ -771,7 +771,7 @@ func TestIncrementUintptr(t *testing.T) {
 }
 
 func TestIncrementUint8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint8", uint8(1), DefaultExpiration)
 	n, err := tc.IncrementUint8("tuint8", 2)
 	if err != nil {
@@ -790,7 +790,7 @@ func TestIncrementUint8(t *testing.T) {
 }
 
 func TestIncrementUint16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint16", uint16(1), DefaultExpiration)
 	n, err := tc.IncrementUint16("tuint16", 2)
 	if err != nil {
@@ -809,7 +809,7 @@ func TestIncrementUint16(t *testing.T) {
 }
 
 func TestIncrementUint32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint32", uint32(1), DefaultExpiration)
 	n, err := tc.IncrementUint32("tuint32", 2)
 	if err != nil {
@@ -828,7 +828,7 @@ func TestIncrementUint32(t *testing.T) {
 }
 
 func TestIncrementUint64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("tuint64", uint64(1), DefaultExpiration)
 	n, err := tc.IncrementUint64("tuint64", 2)
 	if err != nil {
@@ -847,7 +847,7 @@ func TestIncrementUint64(t *testing.T) {
 }
 
 func TestIncrementFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(1.5), DefaultExpiration)
 	n, err := tc.IncrementFloat32("float32", 2)
 	if err != nil {
@@ -866,7 +866,7 @@ func TestIncrementFloat32(t *testing.T) {
 }
 
 func TestIncrementFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(1.5), DefaultExpiration)
 	n, err := tc.IncrementFloat64("float64", 2)
 	if err != nil {
@@ -885,7 +885,7 @@ func TestIncrementFloat64(t *testing.T) {
 }
 
 func TestDecrementInt8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int8", int8(5), DefaultExpiration)
 	n, err := tc.DecrementInt8("int8", 2)
 	if err != nil {
@@ -904,7 +904,7 @@ func TestDecrementInt8(t *testing.T) {
 }
 
 func TestDecrementInt16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int16", int16(5), DefaultExpiration)
 	n, err := tc.DecrementInt16("int16", 2)
 	if err != nil {
@@ -923,7 +923,7 @@ func TestDecrementInt16(t *testing.T) {
 }
 
 func TestDecrementInt32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int32", int32(5), DefaultExpiration)
 	n, err := tc.DecrementInt32("int32", 2)
 	if err != nil {
@@ -942,7 +942,7 @@ func TestDecrementInt32(t *testing.T) {
 }
 
 func TestDecrementInt64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int64", int64(5), DefaultExpiration)
 	n, err := tc.DecrementInt64("int64", 2)
 	if err != nil {
@@ -961,7 +961,7 @@ func TestDecrementInt64(t *testing.T) {
 }
 
 func TestDecrementUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint", uint(5), DefaultExpiration)
 	n, err := tc.DecrementUint("uint", 2)
 	if err != nil {
@@ -980,7 +980,7 @@ func TestDecrementUint(t *testing.T) {
 }
 
 func TestDecrementUintptr(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uintptr", uintptr(5), DefaultExpiration)
 	n, err := tc.DecrementUintptr("uintptr", 2)
 	if err != nil {
@@ -999,7 +999,7 @@ func TestDecrementUintptr(t *testing.T) {
 }
 
 func TestDecrementUint8(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint8", uint8(5), DefaultExpiration)
 	n, err := tc.DecrementUint8("uint8", 2)
 	if err != nil {
@@ -1018,7 +1018,7 @@ func TestDecrementUint8(t *testing.T) {
 }
 
 func TestDecrementUint16(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint16", uint16(5), DefaultExpiration)
 	n, err := tc.DecrementUint16("uint16", 2)
 	if err != nil {
@@ -1037,7 +1037,7 @@ func TestDecrementUint16(t *testing.T) {
 }
 
 func TestDecrementUint32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint32", uint32(5), DefaultExpiration)
 	n, err := tc.DecrementUint32("uint32", 2)
 	if err != nil {
@@ -1056,7 +1056,7 @@ func TestDecrementUint32(t *testing.T) {
 }
 
 func TestDecrementUint64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint64", uint64(5), DefaultExpiration)
 	n, err := tc.DecrementUint64("uint64", 2)
 	if err != nil {
@@ -1075,7 +1075,7 @@ func TestDecrementUint64(t *testing.T) {
 }
 
 func TestDecrementFloat32(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float32", float32(5), DefaultExpiration)
 	n, err := tc.DecrementFloat32("float32", 2)
 	if err != nil {
@@ -1094,7 +1094,7 @@ func TestDecrementFloat32(t *testing.T) {
 }
 
 func TestDecrementFloat64(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("float64", float64(5), DefaultExpiration)
 	n, err := tc.DecrementFloat64("float64", 2)
 	if err != nil {
@@ -1113,7 +1113,7 @@ func TestDecrementFloat64(t *testing.T) {
 }
 
 func TestAdd(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	err := tc.Add("foo", "bar", DefaultExpiration)
 	if err != nil {
 		t.Error("Couldn't add foo even though it shouldn't exist")
@@ -1125,7 +1125,7 @@ func TestAdd(t *testing.T) {
 }
 
 func TestReplace(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	err := tc.Replace("foo", "bar", DefaultExpiration)
 	if err == nil {
 		t.Error("Replaced foo when it shouldn't exist")
@@ -1138,7 +1138,7 @@ func TestReplace(t *testing.T) {
 }
 
 func TestDelete(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", "bar", DefaultExpiration)
 	tc.Delete("foo")
 	x, found := tc.Get("foo")
@@ -1151,7 +1151,7 @@ func TestDelete(t *testing.T) {
 }
 
 func TestItemCount(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", "1", DefaultExpiration)
 	tc.Set("bar", "2", DefaultExpiration)
 	tc.Set("baz", "3", DefaultExpiration)
@@ -1161,7 +1161,7 @@ func TestItemCount(t *testing.T) {
 }
 
 func TestFlush(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", "bar", DefaultExpiration)
 	tc.Set("baz", "yes", DefaultExpiration)
 	tc.Flush()
@@ -1182,7 +1182,7 @@ func TestFlush(t *testing.T) {
 }
 
 func TestIncrementOverflowInt(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("int8", int8(127), DefaultExpiration)
 	err := tc.Increment("int8", 1)
 	if err != nil {
@@ -1197,7 +1197,7 @@ func TestIncrementOverflowInt(t *testing.T) {
 }
 
 func TestIncrementOverflowUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint8", uint8(255), DefaultExpiration)
 	err := tc.Increment("uint8", 1)
 	if err != nil {
@@ -1211,7 +1211,7 @@ func TestIncrementOverflowUint(t *testing.T) {
 }
 
 func TestDecrementUnderflowUint(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("uint8", uint8(0), DefaultExpiration)
 	err := tc.Decrement("uint8", 1)
 	if err != nil {
@@ -1225,7 +1225,7 @@ func TestDecrementUnderflowUint(t *testing.T) {
 }
 
 func TestCacheSerialization(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	testFillAndSerialize(t, tc)
 
 	// Check if gob.Register behaves properly even after multiple gob.Register
@@ -1261,7 +1261,7 @@ func testFillAndSerialize(t *testing.T, tc *Cache) {
 		t.Fatal("Couldn't save cache to fp:", err)
 	}
 
-	oc := New(DefaultExpiration, 0)
+	oc := New(DefaultExpiration, 0, 0)
 	err = oc.Load(fp)
 	if err != nil {
 		t.Fatal("Couldn't load cache from fp:", err)
@@ -1352,7 +1352,7 @@ func testFillAndSerialize(t *testing.T, tc *Cache) {
 }
 
 func TestFileSerialization(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Add("a", "a", DefaultExpiration)
 	tc.Add("b", "b", DefaultExpiration)
 	f, err := ioutil.TempFile("", "go-cache-cache.dat")
@@ -1363,7 +1363,7 @@ func TestFileSerialization(t *testing.T) {
 	f.Close()
 	tc.SaveFile(fname)
 
-	oc := New(DefaultExpiration, 0)
+	oc := New(DefaultExpiration, 0, 0)
 	oc.Add("a", "aa", 0) // this should not be overwritten
 	err = oc.LoadFile(fname)
 	if err != nil {
@@ -1391,7 +1391,7 @@ func TestFileSerialization(t *testing.T) {
 }
 
 func TestSerializeUnserializable(t *testing.T) {
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	ch := make(chan bool, 1)
 	ch <- true
 	tc.Set("chan", ch, DefaultExpiration)
@@ -1404,7 +1404,7 @@ func TestSerializeUnserializable(t *testing.T) {
 
 func BenchmarkCacheGet(b *testing.B) {
 	b.StopTimer()
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", "bar", DefaultExpiration)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
@@ -1428,7 +1428,7 @@ func BenchmarkRWMutexMapGet(b *testing.B) {
 
 func BenchmarkCacheGetConcurrent(b *testing.B) {
 	b.StopTimer()
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	tc.Set("foo", "bar", DefaultExpiration)
 	wg := new(sync.WaitGroup)
 	workers := runtime.NumCPU()
@@ -1476,7 +1476,7 @@ func BenchmarkCacheGetManyConcurrent(b *testing.B) {
 	// in sharded_test.go.
 	b.StopTimer()
 	n := 10000
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	keys := make([]string, n)
 	for i := 0; i < n; i++ {
 		k := "foo" + strconv.Itoa(n)
@@ -1500,7 +1500,7 @@ func BenchmarkCacheGetManyConcurrent(b *testing.B) {
 
 func BenchmarkCacheSet(b *testing.B) {
 	b.StopTimer()
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		tc.Set("foo", "bar", DefaultExpiration)
@@ -1521,7 +1521,7 @@ func BenchmarkRWMutexMapSet(b *testing.B) {
 
 func BenchmarkCacheSetDelete(b *testing.B) {
 	b.StopTimer()
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		tc.Set("foo", "bar", DefaultExpiration)
@@ -1546,7 +1546,7 @@ func BenchmarkRWMutexMapSetDelete(b *testing.B) {
 
 func BenchmarkCacheSetDeleteSingleLock(b *testing.B) {
 	b.StopTimer()
-	tc := New(DefaultExpiration, 0)
+	tc := New(DefaultExpiration, 0, 0)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		tc.Lock()