[core] gobot.Every function now returns a channel so it can be halted

Signed-off-by: deadprogram <ron@hybridgroup.com>

utils.go

@@ -23,17 +23,27 @@ var eventError = func(e *Event) (err error) {
 	return
 }
 
-// Every triggers f every t time until the end of days. It does not wait for the
+// Every triggers f every t time until the end of days, or when a
-// previous execution of f to finish before it fires the next f.
+// bool value is sent to the channel returned by the Every function.
-func Every(t time.Duration, f func()) {
+// It does not wait for the previous execution of f to finish before
+// it fires the next f.
+func Every(t time.Duration, f func()) chan bool {
+	done := make(chan bool)
 	c := time.Tick(t)
 
 	go func() {
 		for {
+			select {
+			case <-done:
+				break
+			default:
 				<-c
 				go f()
 			}
+		}
 	}()
+
+	return done
 }
 
 // After triggers f after t duration.

utils_test.go

@@ -24,6 +24,18 @@ func TestEvery(t *testing.T) {
 	}
 }
 
+func TestEveryWhenDone(t *testing.T) {
+	i := 0
+	done := Every(20*time.Millisecond, func() {
+		i++
+	})
+	<-time.After(20 * time.Millisecond)
+	done <- true
+	if i > 1 {
+		t.Error("Test should have stopped after 20ms")
+	}
+}
+
 func TestAfter(t *testing.T) {
 	i := 0
 	After(1*time.Millisecond, func() {