code: void release(final Channel channel) {
          if (this.executor.inEventLoop()) {
              this.releaseWithinEventExecutor(channel);
          } else {
              this.executor.submit(new Runnable() {
                  @Override
                  public void run() {
                      ApnsChannelPool.this.releaseWithinEventExecutor(channel);
                  }
              });
          }
      }
docs: Returns a previously-acquired channel to the pool.
  
  @param channel the channel to return to the pool