code: public void releaseMessage(String id, String reservationId, Long delay) throws IOException {
          String url = "queues/" + name + "/messages/" + id + "/release";
          String payload = gson.toJson(new MessageOptions(reservationId, delay));
          IronReader reader = client.post(url, payload);
          reader.close();
      }
docs: Release reserved message after specified time. If there is no message with such id on the queue, an
  EmptyQueueException is thrown.
  
  @param id The ID of the message to release.
  @param delay The time after which the message will be released.
  
  @throws io.iron.ironmq.HTTPException If the IronMQ service returns a status other than 200 OK.
  @throws java.io.IOException If there is an error accessing the IronMQ server.