time: add an example to the NewTicker function

Change-Id: Idad9cdee36679373ee223ff2bd4c021ea0afcce1
Reviewed-on: https://go-review.googlesource.com/61710
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/time/example_test.go

@@ -127,6 +127,25 @@ func ExampleDate() {
 	// Output: Go launched at 2009-11-10 15:00:00 -0800 PST
 }
 
+func ExampleNewTicker() {
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
+	done := make(chan bool)
+	go func() {
+		time.Sleep(10 * time.Second)
+		done <- true
+	}()
+	for {
+		select {
+		case <-done:
+			fmt.Println("Done!")
+			return
+		case t := <-ticker.C:
+			fmt.Println("Current time: ", t)
+		}
+	}
+}
+
 func ExampleTime_Format() {
 	// Parse a time value from a string in the standard Unix format.
 	t, err := time.Parse(time.UnixDate, "Sat Mar  7 11:06:39 PST 2015")