code: func (rtm *RTM) handlePong(event json.RawMessage) {
  	var (
  		p Pong
  	)
  
  	rtm.resetDeadman()
  
  	if err := json.Unmarshal(event, &p); err != nil {
  		rtm.Client.log.Println("RTM Error unmarshalling 'pong' event:", err)
  		return
  	}
  
  	latency := time.Since(time.Unix(p.Timestamp, 0))
  	rtm.IncomingEvents <- RTMEvent{"latency_report", &LatencyReport{Value: latency}}
  }
docs: // handlePong handles an incoming 'PONG' message which should be in response to
  // a previously sent 'PING' message. This is then used to compute the
  // connection's latency.