code: func ExtractHostID(id string) (string, error) {
  	ids := strings.SplitN(id, "-", 2)
  	if len(ids) != 2 || ids[0] == "" || ids[1] == "" {
  		return "", errors.New("invalid ID")
  	}
  	return ids[0], nil
  }
docs: // ExtractHostID returns the host ID component of a job ID, returning an error
  // if the given ID is invalid.