// A common use case is to get a private config folder for your app to
// place its settings files into, that are specific to the local user.
configPath := configdir.LocalConfig("my-app")
err := configdir.MakePath(configPath) // Ensure it exists.
if err != nil {
    panic(err)
}

// Deal with a JSON configuration file in that folder.
configFile := filepath.Join(configPath, "settings.json")
type AppSettings struct {
    Username string `json:"username"`
    Password string `json:"password"`
}
var settings AppSettings

// Does the file not exist?
if _, err = os.Stat(configFile); os.IsNotExist(err) {
    // Create the new config file.
    settings = AppSettings{"MyUser", "MyPassword"}
    fh, err := os.Create(configFile)
    if err != nil {
        panic(err)
    }
    defer fh.Close()

    encoder := json.NewEncoder(fh)
    encoder.Encode(&settings)
} else {
    // Load the existing file.
    fh, err := os.Open(configFile)
    if err != nil {
        panic(err)
    }
    defer fh.Close()

    decoder := json.NewDecoder(fh)
    decoder.Decode(&settings)
}