Fix data race for config with FileSource (#26518)

Signed-off-by: yah01 <yah2er0ne@outlook.com>

pkg/config/file_source.go

@@ -91,6 +91,8 @@ func (fs *FileSource) Close() {
 }
 
 func (fs *FileSource) SetEventHandler(eh EventHandler) {
+	fs.RWMutex.Lock()
+	defer fs.RWMutex.Unlock()
 	fs.configRefresher.eh = eh
 }
 

pkg/config/refresher.go

@@ -86,7 +86,7 @@ func (r *refresher) fireEvents(name string, source, target map[string]string) er
 		log.Warn("generating event error", zap.Error(err))
 		return err
 	}
-	//Generate OnEvent Callback based on the events created
+	// Generate OnEvent Callback based on the events created
 	if r.eh != nil {
 		for _, e := range events {
 			r.eh.OnEvent(e)