code: func XDGBaseDir(configFileName string) *configSource {
  	skip := false
  	// Look for config in standard XDG specified locations
  	configFile, err := xdgbasedir.GetConfigFileLocation(configFileName)
  	if err == nil {
  		_, err := os.Stat(configFile)
  		// Skip if config  file does not exist at default location
  		skip = os.IsNotExist(err)
  	}
  	return &configSource{
  		skip: skip,
  		from: fmt.Sprintf("XDG base dir"),
  		apply: func(baseConfig interface{}) error {
  			if err != nil {
  				return err
  			}
  			return FromFile(configFile, baseConfig)
  		},
  	}
  }
docs: // Try to find config by using XDG base dir spec