From c6ec2c669fc9fd94a3a6ad9ab8f8095b441cf32c Mon Sep 17 00:00:00 2001
From: mzz2017 <m@mzz.pub>
Date: Fri, 1 Jan 2021 18:36:33 +0800
Subject: [PATCH] fix: a potential concurrency problem

---
 main.go | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/main.go b/main.go
index 36dbd45..0380a22 100644
--- a/main.go
+++ b/main.go
@@ -27,11 +27,6 @@ func main() {
 }
 
 func listen(group *config.Group) {
-	mMutex.Lock()
-	if _, ok := mPortDispatcher[group.Port]; !ok {
-		mPortDispatcher[group.Port] = new([2]dispatcher.Dispatcher)
-	}
-	mMutex.Unlock()
 	err := listenWithProtocols(group, protocols[:])
 	if err != nil {
 		mMutex.Lock()
@@ -45,10 +40,17 @@ func listen(group *config.Group) {
 }
 
 func listenWithProtocols(group *config.Group, protocols []string) error {
+	mMutex.Lock()
+	if _, ok := mPortDispatcher[group.Port]; !ok {
+		mPortDispatcher[group.Port] = new([2]dispatcher.Dispatcher)
+	}
+	t := mPortDispatcher[group.Port]
+	mMutex.Unlock()
+
 	ch := make(chan error, len(protocols))
 	for i, protocol := range protocols {
 		d, _ := dispatcher.New(protocol, group)
-		(*mPortDispatcher[group.Port])[i] = d
+		(*t)[i] = d
 		go func() {
 			var err error
 			err = d.Listen()