add client closechan

pkg/mqtt/connection.go

@@ -130,8 +130,9 @@ func (c *Connection) Close() {
 	if c.SendChan != nil {
 		close(c.SendChan)
 		c.SendChan = nil
+		close(c.closeChan)
 	}
-	close(c.closeChan)
+
 }
 
 func (c *Connection) RcvMsgFromClient() {