code: @Override
      public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
          registeredFutureLatch.reset();
          ScheduledFuture<?> future = keepAliveFuture.get();
          if (future != null) {
              future.cancel(false);
          }
          channel.set(null);
          flowIdReplyProcessorMap.forEach((flowId, rp) -> {
              rp.connectionDropped();
              log.debug("Connection dropped for flow id {}", flowId);
          });
          super.channelUnregistered(ctx);
      }
docs: Invoke all the {@link ReplyProcessor#connectionDropped()} for all the registered flows once the
  connection is disconnected.
  
  @see io.netty.channel.ChannelInboundHandler#channelUnregistered(ChannelHandlerContext)