How Do I Parse a JSON file into a struct with Go

Question

I'm trying to configure my Go program by creating a JSON file and parsing it into a struct:

var settings struct {     serverMode bool     sourceDir  string     targetDir  string }  func main() {      // then config file settings      configFile, err := os.Open("config.json")     if err != nil {         printError("opening config file", err.Error())     }      jsonParser := json.NewDecoder(configFile)     if err = jsonParser.Decode(&settings); err != nil {         printError("parsing config file", err.Error())     }      fmt.Printf("%v %s %s", settings.serverMode, settings.sourceDir, settings.targetDir)     return } 

The config.json file:

{     "serverMode": true,     "sourceDir": ".",     "targetDir": "." } 

The Program compiles and runs without any errors, but the print statement outputs:

false   

(false and two empty strings)

I've also tried with json.Unmarshal(..) but had the same result.

How do I parse the JSON in a way that fills the struct values?

Answer 1

You're not exporting your struct elements. They all begin with a lower case letter.

var settings struct {     ServerMode bool `json:"serverMode"`     SourceDir  string `json:"sourceDir"`     TargetDir  string `json:"targetDir"` } 

Make the first letter of your stuct elements upper case to export them. The JSON encoder/decoder wont use struct elements which are not exported.