code: func (r *RoundRobinResponseWriter) WriteMsg(res *dns.Msg) error {
  	if res.Rcode != dns.RcodeSuccess {
  		return r.ResponseWriter.WriteMsg(res)
  	}
  
  	res.Answer = roundRobin(res.Answer)
  	res.Ns = roundRobin(res.Ns)
  	res.Extra = roundRobin(res.Extra)
  
  	return r.ResponseWriter.WriteMsg(res)
  }
docs: // WriteMsg implements the dns.ResponseWriter interface.