diff --git a/gnet.go b/gnet.go
index 047b4ef98..fd3098913 100644
--- a/gnet.go
+++ b/gnet.go
@@ -226,6 +226,12 @@ type Writer interface {
 	// AsyncWrite writes bytes to peer asynchronously, it's goroutine-safe,
 	// you don't have to invoke it within any method in EventHandler,
 	// usually you would call it in an individual goroutine.
+	//
+	// Note that it will go synchronously with UDP, so it is needless to call
+	// this asynchronous method, we may disable this method for UDP and just
+	// return ErrUnsupportedOp in the future, therefore, please don't rely on
+	// this method to do something important under UDP, if you're working with UDP,
+	// just call Conn.Write to send back your data.
 	AsyncWrite(buf []byte, callback AsyncCallback) (err error)
 
 	// AsyncWritev writes multiple byte slices to peer asynchronously,
diff --git a/gnet_test.go b/gnet_test.go
index abf5ee569..927dbad95 100644
--- a/gnet_test.go
+++ b/gnet_test.go
@@ -552,6 +552,11 @@ func (t *testWakeConnServer) OnTick() (delay time.Duration, action Action) {
 }
 
 func testWakeConn(t *testing.T, network, addr string) {
+	currentLogger, currentFlusher := logging.GetDefaultLogger(), logging.GetDefaultFlusher()
+	t.Cleanup(func() {
+		logging.SetDefaultLoggerAndFlusher(currentLogger, currentFlusher) // restore
+	})
+
 	svr := &testWakeConnServer{tester: t, network: network, addr: addr, conn: make(chan Conn, 1)}
 	logger := zap.NewExample()
 	err := Run(svr, network+"://"+addr,
@@ -1145,6 +1150,11 @@ func (t *testMultiInstLoggerRaceServer) OnBoot(_ Engine) (action Action) {
 }
 
 func TestMultiInstLoggerRace(t *testing.T) {
+	currentLogger, currentFlusher := logging.GetDefaultLogger(), logging.GetDefaultFlusher()
+	t.Cleanup(func() {
+		logging.SetDefaultLoggerAndFlusher(currentLogger, currentFlusher) // restore
+	})
+
 	logger1, _ := zap.NewDevelopment()
 	events1 := new(testMultiInstLoggerRaceServer)
 	g := errgroup.Group{}