feat: add watcher for record code excution time

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)
+	}
+}

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))
+	}
+}