etcdClient, err := clientv3.New(cfg)
	if err != nil {
		return nil, err
	}

	args := &CoreDNS{
		etcdClient: etcdClient,
	}

	for _, setter := range setters {
		setter(args)
	}

	if len(args.domainNames) == 0 || args.domainIPs.IsEmpty() {
		return nil, errors.New("invalid argument")
	}

	// strip ports off of domainIPs

	if endpoint == "" {
		return nil, errors.New("invalid argument")
	}

	args := &OperatorDNS{
		Endpoint: endpoint,
	}
	for _, setter := range setters {
		setter(args)
	}
	args.httpClient = &http.Client{
		Transport: &http.Transport{
			Proxy: http.ProxyFromEnvironment,
			DialContext: (&net.Dialer{
				Timeout:   3 * time.Second,