code: func (s *StreamReader) LongPoll(seconds int) {
  	if seconds > 0 {
  		s.client.SetHeader("ES-LongPoll", strconv.Itoa(seconds))
  	} else {
  		s.client.DeleteHeader("ES-LongPoll")
  	}
  }
docs: // LongPoll causes the server to wait up to the number of seconds specified
  // for results to become available at the URL requested.
  //
  // LongPoll is useful when polling the end of the stream as it returns quickly
  // after new events are found which means that it is more responsive than polling
  // over some arbitrary time interval. It also reduces the number of
  // unproductive calls to the server polling for events when there are no new
  // events to return.
  //
  // Setting the argument seconds to any integer value above 0 will cause the
  // request to be made with ES-LongPoll set to that value. Any value 0 or below
  // will cause the request to be made without ES-LongPoll and the server will not
  // wait to return.