use atomic.(Load|Store)Int64 for requestTimeout

conn.go

@@ -194,9 +194,7 @@ func (l *Conn) Close() {
 // SetTimeout sets the time after a request is sent that a MessageTimeout triggers
 func (l *Conn) SetTimeout(timeout time.Duration) {
 	if timeout > 0 {
-		l.timeoutMutex.Lock()
-		l.requestTimeout = timeout
-		l.timeoutMutex.Unlock()
+		atomic.StoreInt64((*int64)(&l.requestTimeout), int64(timeout))
 	}
 }
 
@@ -391,9 +389,7 @@ func (l *Conn) processMessages() {
 				l.messageContexts[message.MessageID] = message.Context
 
 				// Add timeout if defined
-				l.timeoutMutex.Lock()
-				to := l.requestTimeout
-				l.timeoutMutex.Unlock()
+				to := time.Duration(atomic.LoadInt64((*int64)(&l.requestTimeout)))
 				if to > 0 {
 					go func() {
 						defer func() {