Guard Peek call with mutex for thread safety

Author: ofekshenawa

command.go

@@ -5454,8 +5454,9 @@ func (cmd *MonitorCmd) readMonitor(rd *proto.Reader, cancel context.CancelFunc)
 	for {
 		cmd.mu.Lock()
 		st := cmd.status
+		pk, _ := rd.Peek(1)
 		cmd.mu.Unlock()
-		if pk, _ := rd.Peek(1); len(pk) != 0 && st == monitorStatusStart {
+		if len(pk) != 0 && st == monitorStatusStart {
 			cmd.mu.Lock()
 			line, err := rd.ReadString()
 			cmd.mu.Unlock()