code: func parseEnsAPIAddress(s string) (tld, endpoint string, addr common.Address) {
  	isAllLetterString := func(s string) bool {
  		for _, r := range s {
  			if !unicode.IsLetter(r) {
  				return false
  			}
  		}
  		return true
  	}
  	endpoint = s
  	if i := strings.Index(endpoint, ":"); i > 0 {
  		if isAllLetterString(endpoint[:i]) && len(endpoint) > i+2 && endpoint[i+1:i+3] != "//" {
  			tld = endpoint[:i]
  			endpoint = endpoint[i+1:]
  		}
  	}
  	if i := strings.Index(endpoint, "@"); i > 0 {
  		addr = common.HexToAddress(endpoint[:i])
  		endpoint = endpoint[i+1:]
  	}
  	return
  }
docs: // parseEnsAPIAddress parses string according to format
  // [tld:][contract-addr@]url and returns ENSClientConfig structure
  // with endpoint, contract address and TLD.