code: @Override
      public void onBeforeClose(ChannelContext channelContext, Throwable throwable, String remark, boolean isRemove) {
          log.debug("连接关闭前触发onBeforeClose");
      }
docs: 连接关闭前触发本方法
  
  @param channelContext the channelcontext
  @param throwable the throwable 有可能为空
  @param remark the remark 有可能为空
  @param isRemove
  @author tanyaowu