code: func (c *Certifier) checkResponse(order acme.Order, certRes *Resource, bundle bool) (bool, error) {
  	valid, err := checkOrderStatus(order)
  	if err != nil || !valid {
  		return valid, err
  	}
  
  	cert, issuer, err := c.core.Certificates.Get(order.Certificate, bundle)
  	if err != nil {
  		return false, err
  	}
  
  	log.Infof("[%s] Server responded with a certificate.", certRes.Domain)
  
  	certRes.IssuerCertificate = issuer
  	certRes.Certificate = cert
  	certRes.CertURL = order.Certificate
  	certRes.CertStableURL = order.Certificate
  
  	return true, nil
  }
docs: // checkResponse checks to see if the certificate is ready and a link is contained in the response.
  //
  // If so, loads it into certRes and returns true.
  // If the cert is not yet ready, it returns false.
  //
  // The certRes input should already have the Domain (common name) field populated.
  //
  // If bundle is true, the certificate will be bundled with the issuer's cert.