diff --git a/function/watcher.go b/function/watcher.go
new file mode 100644
index 0000000..c7a0b6c
--- /dev/null
+++ b/function/watcher.go
@@ -0,0 +1,30 @@
+package function
+
+import "time"
+
+// Watcher is used for record code excution time
+type Watcher struct {
+	startTime int64
+	stopTime  int64
+	excuting  bool
+}
+
+// Start the watch timer.
+func (w *Watcher) Start() {
+	w.startTime = time.Now().UnixNano()
+	w.excuting = true
+}
+
+// Stop the watch timer.
+func (w *Watcher) Stop() {
+	w.stopTime = time.Now().UnixNano()
+	w.excuting = false
+}
+// GetElapsedTime get excute elapsed time.
+func (w *Watcher) GetElapsedTime() time.Duration {
+	if w.excuting {
+		return time.Duration(time.Now().UnixNano() - w.startTime)
+	} else {
+		return time.Duration(w.stopTime - w.startTime)
+	}
+}
\ No newline at end of file
diff --git a/function/watcher_test.go b/function/watcher_test.go
new file mode 100644
index 0000000..dec36eb
--- /dev/null
+++ b/function/watcher_test.go
@@ -0,0 +1,32 @@
+package function
+
+import (
+	"testing"
+)
+
+func TestWatcher(t *testing.T) {
+	w := &Watcher{}
+	w.Start()
+
+	longRunningTask()
+
+	if !w.excuting {
+		t.FailNow()
+	}
+
+	w.Stop()
+
+	eapsedTime := w.GetElapsedTime().Milliseconds()
+	t.Log("Elapsed Time (milsecond)", eapsedTime)
+
+	if w.excuting {
+		t.FailNow()
+	}
+}
+
+func longRunningTask() {
+	var slice []int64
+	for i := 0; i < 10000000; i++ {
+		slice = append(slice, int64(i))
+	}
+}
diff --git a/slice/slice_test.go b/slice/slice_test.go
index 690f6f2..ae2076f 100644
--- a/slice/slice_test.go
+++ b/slice/slice_test.go
@@ -563,6 +563,7 @@ func TestWithout(t *testing.T) {
 func TestShuffle(t *testing.T) {
 	s := []int{1, 2, 3, 4, 5}
 	res := Shuffle(s)
+	t.Log("Shuffle result: ", res)
 
 	if reflect.TypeOf(s) != reflect.TypeOf(res) {
 		internal.LogFailedTestInfo(t, "Shuffle", s, res, res)