provider/coredns.go
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
}
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
}
// NewCoreDNSProvider is a CoreDNS provider constructor