code: public static ChannelFuture shutdownOutput(Channel channel) {
          ChannelFuture future = future(channel);
          channel.getPipeline().sendDownstream(
                  new DownstreamShutdownOutputEvent(channel, future));
          return future;
      }
docs: Sends a {@code "shutdownOutput"} request to the last
  {@link ChannelDownstreamHandler} in the {@link ChannelPipeline} of
  the specified {@link Channel}.
  
  @param channel  the channel to bind
  
  @return the {@link ChannelFuture} which will be notified when the
  shutdownOutput operation is done