code: func UserConfigDir() string {
  	xdgConfigHome := os.Getenv("XDG_CONFIG_HOME")
  	if xdgConfigHome != "" {
  		return filepath.Join(xdgConfigHome, "buildkit")
  	}
  	home := os.Getenv("HOME")
  	if home != "" {
  		return filepath.Join(home, ".config", "buildkit")
  	}
  	return ConfigDir
  }
docs: // UserConfigDir returns dir for storing config. /home/$USER/.config/buildkit/