code: func ParsePort(port string) (int, error) {
  	portInt, err := strconv.Atoi(port)
  	if err == nil && (1 <= portInt && portInt <= 65535) {
  		return portInt, nil
  	}
  
  	return 0, errors.New("port must be a valid number between 1 and 65535, inclusive")
  }
docs: // ParsePort parses a string representing a TCP port.
  // If the string is not a valid representation of a TCP port, ParsePort returns an error.