init

main.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+)
+
+func expensive(worker int, task string) error {
+	time.Sleep(250 * time.Millisecond)
+	return fmt.Errorf("worker %d is done with %q", worker, task)
+}
+
+func worker(id int, work chan string, results chan error, wg *sync.WaitGroup) {
+	defer wg.Done()
+	for {
+		i, ok := <-work
+		if !ok {
+			return
+		}
+		results <- expensive(id, i)
+	}
+}
+
+func main() {
+	work := make(chan string)
+	results := make(chan error)
+
+	numWorkers := 4
+	wwg := &sync.WaitGroup{}
+	wg := &sync.WaitGroup{}
+	for w := 0; w < numWorkers; w++ {
+		wwg.Add(1)
+		go worker(w, work, results, wwg)
+	}
+
+	s := bufio.NewScanner(os.Stdin)
+	go func(wg *sync.WaitGroup) {
+		for s.Scan() {
+			wg.Add(1)
+			work <- s.Text()
+		}
+		if err := s.Err(); err != nil {
+			panic(err)
+		}
+		close(work)
+	}(wg)
+
+	go func() {
+		wwg.Wait()
+		wg.Wait()
+		close(results)
+	}()
+
+	for e := range results {
+		fmt.Printf("received: %+v\n", e)
+		wg.Done()
+	}
+}