code: func (c *CertificateService) Get(certURL string, bundle bool) ([]byte, []byte, error) {
  	cert, up, err := c.get(certURL)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	// Get issuerCert from bundled response from Let's Encrypt
  	// See https://community.letsencrypt.org/t/acme-v2-no-up-link-in-response/64962
  	_, issuer := pem.Decode(cert)
  	if issuer != nil {
  		return cert, issuer, nil
  	}
  
  	issuer, err = c.getIssuerFromLink(up)
  	if err != nil {
  		// If we fail to acquire the issuer cert, return the issued certificate - do not fail.
  		log.Warnf("acme: Could not bundle issuer certificate [%s]: %v", certURL, err)
  	} else if len(issuer) > 0 {
  		// If bundle is true, we want to return a certificate bundle.
  		// To do this, we append the issuer cert to the issued cert.
  		if bundle {
  			cert = append(cert, issuer...)
  		}
  	}
  
  	return cert, issuer, nil
  }
docs: // Get Returns the certificate and the issuer certificate.
  // 'bundle' is only applied if the issuer is provided by the 'up' link.