code: func (hc *PingChecker) Check(timeout time.Duration) *Result {
  	msg := fmt.Sprintf("ICMP ping to host %v", hc.IP)
  	seq := hc.Seqnum
  	hc.Seqnum++
  	echo := newICMPEchoRequest(hc.Proto, hc.ID, seq, 64, []byte("Healthcheck"))
  	start := time.Now()
  	if timeout == time.Duration(0) {
  		timeout = defaultPingTimeout
  	}
  	err := exchangeICMPEcho(hc.network(), hc.IP, timeout, echo)
  	success := err == nil
  	return complete(start, msg, success, err)
  }
docs: // Check executes a ping healthcheck.