code: func GetRecord(domain, keyAuth string) (fqdn string, value string) {
  	keyAuthShaBytes := sha256.Sum256([]byte(keyAuth))
  	// base64URL encoding without padding
  	value = base64.RawURLEncoding.EncodeToString(keyAuthShaBytes[:sha256.Size])
  	fqdn = fmt.Sprintf("_acme-challenge.%s.", domain)
  
  	if ok, _ := strconv.ParseBool(os.Getenv("LEGO_EXPERIMENTAL_CNAME_SUPPORT")); ok {
  		r, err := dnsQuery(fqdn, dns.TypeCNAME, recursiveNameservers, true)
  		// Check if the domain has CNAME then return that
  		if err == nil && r.Rcode == dns.RcodeSuccess {
  			fqdn = updateDomainWithCName(r, fqdn)
  		}
  	}
  
  	return
  }
docs: // GetRecord returns a DNS record which will fulfill the `dns-01` challenge