Update to gobook@c6d7a22edd03e7738c38d5baa2174ff325d8d863

ch1/lissajous/main.go

@@ -13,17 +13,21 @@ import (
 	"image/color"
 	"image/gif"
 	"io"
-	//!-main
-	"log"
-	//!+main
 	"math"
 	"math/rand"
-	//!-main
-	"net/http"
-	//!+main
 	"os"
 )
 
+//!-main
+// Packages not needed by version in book.
+import (
+	"log"
+	"net/http"
+	"time"
+)
+
+//!+main
+
 var palette = []color.Color{color.White, color.Black}
 
 const (
@@ -33,6 +37,11 @@ const (
 
 func main() {
 	//!-main
+	// The sequence of images is deterministic unless we seed
+	// the pseudo-random number generator using the current time.
+	// Thanks to Randall McPherson for pointing out the omission.
+	rand.Seed(time.Now().UTC().UnixNano())
+
 	if len(os.Args) > 1 && os.Args[1] == "web" {
 		//!+http
 		handler := func(w http.ResponseWriter, r *http.Request) {