code: func NewCoreDNSProvider(domainFilter DomainFilter, dryRun bool) (Provider, error) {
  	client, err := newETCDClient()
  	if err != nil {
  		return nil, err
  	}
  	return coreDNSProvider{
  		client:       client,
  		dryRun:       dryRun,
  		domainFilter: domainFilter,
  	}, nil
  }
docs: // NewCoreDNSProvider is a CoreDNS provider constructor