code: func normalizeDNSName(dnsName string) string {
  	s := strings.TrimSpace(strings.ToLower(dnsName))
  	if !strings.HasSuffix(s, ".") {
  		s += "."
  	}
  	return s
  }
docs: // normalizeDNSName converts a DNS name to a canonical form, so that we can use string equality
  // it: removes space, converts to lower case, ensures there is a trailing dot