code: func Revoke(host string) error {
  	client, err := newACMEClient(new(Config), true)
  	if err != nil {
  		return err
  	}
  	return client.Revoke(host)
  }
docs: // Revoke revokes the certificate for host via ACME protocol.
  // It assumes the certificate was obtained from the
  // CA at DefaultCAUrl.