code: func parseSimpleProtoAddr(proto, addr, defaultAddr string) (string, error) {
  	addr = strings.TrimPrefix(addr, proto+"://")
  	if strings.Contains(addr, "://") {
  		return "", fmt.Errorf("Invalid proto, expected %s: %s", proto, addr)
  	}
  	if addr == "" {
  		addr = defaultAddr
  	}
  	return fmt.Sprintf("%s://%s", proto, addr), nil
  }
docs: // parseSimpleProtoAddr parses and validates that the specified address is a valid
  // socket address for simple protocols like unix and npipe. It returns a formatted
  // socket address, either using the address parsed from addr, or the contents of
  // defaultAddr if addr is a blank string.