fix data race issues

common/stats/session/session.go

@@ -93,11 +93,8 @@ func (s *simpleSessionStater) Start() error {
 		http.Redirect(w, r, StatsPath, 301)
 	})
 	mux.HandleFunc(StatsPath, sessionStatsHandler)
-	server := &http.Server{Addr: StatsAddr, Handler: mux}
-	s.server = server
-	go func() {
-		_ = s.server.ListenAndServe()
-	}()
+	s.server = &http.Server{Addr: StatsAddr, Handler: mux}
+	go s.server.ListenAndServe()
 	return nil
 }
 
@@ -118,14 +115,14 @@ func (s *simpleSessionStater) GetSession(key interface{}) *stats.Session {
 }
 
 func (s *simpleSessionStater) RemoveSession(key interface{}) {
+	s.mux.Lock()
+	defer s.mux.Unlock()
+
 	if sess, ok := s.sessions.Load(key); ok {
-		// temporary workaround for slice race condition
-		s.mux.Lock()
 		s.completedSessions = append(s.completedSessions, *(sess.(*stats.Session)))
 		if len(s.completedSessions) > maxCompletedSessions {
 			s.completedSessions = s.completedSessions[1:]
 		}
-		s.mux.Unlock()
 	}
 	s.sessions.Delete(key)
 }

proxy/socks/tcp.go

@@ -84,7 +84,6 @@ type duplexConn interface {
 }
 
 func (h *tcpHandler) relay(lhs, rhs net.Conn, sess *stats.Session) {
-	var err error
 	upCh := make(chan struct{})
 
 	cls := func(dir direction, interrupt bool) {
@@ -109,6 +108,7 @@ func (h *tcpHandler) relay(lhs, rhs net.Conn, sess *stats.Session) {
 
 	// Uplink
 	go func() {
+		var err error
 		if h.sessionStater != nil && sess != nil {
 			_, err = statsCopy(rhs, lhs, sess, dirUplink)
 		} else {
@@ -123,6 +123,7 @@ func (h *tcpHandler) relay(lhs, rhs net.Conn, sess *stats.Session) {
 	}()
 
 	// Downlink
+	var err error
 	if h.sessionStater != nil && sess != nil {
 		_, err = statsCopy(lhs, rhs, sess, dirDownlink)
 	} else {