How we can read a JSON file with Go Programming Language?

Question

I'm working on a translation project on my Angular app. I already create all the different keys for that. I try now to use Go Programming Language to add some functionalities in my translation, to work quickly after.

I try to code a function in Go Programming Language in order to read an input user on the command line. I need to read this input file in order to know if there is missing key inside. This input user must be a JSON file. I have a problem with this function, is blocked at functions.Check(err), in order to debug my function I displayed the different variable with fmt.Printf(variable to display). I call this function readInput() in my main function.

The readInput() function is the following :

    // this function is used to read the user's input on the command line
func readInput() string {
    // we create a reader
    reader := bufio.NewReader(os.Stdin)
    // we read the user's input
    answer, err := reader.ReadString('\n')
    // we check if any errors have occured while reading
    functions.Check(err)
    // we trim the "\n" from the answer to only keep the string input by the user
    answer = strings.Trim(answer, "\n")
    return answer
}

In my main function I call readInput() for a specific command I created. This command line is usefull to update a JSON file and add a missing key automatically.

My func main is :

      func main() { 
        if os.Args[1] == "update-json-from-json" {

    fmt.Printf("please enter the name of the json file that will be used to 
    update the json file:") 
    jsonFile := readInput()

    fmt.Printf("please enter the ISO code of the locale for which you want to update the json file: ")
            // we read the user's input
            locale := readInput()
            // we launch the script
            scripts.AddMissingKeysToJsonFromJson(jsonFile, locale)
        }

I can give you the command line I use for this code go run mis-t.go update-json-from-json

Do you what I'm missing in my code please ?

just google golang json the package and its documentation will be the first result. i do not know how you did not find it — Pizza lord
– Pizza lord, Commented Mar 5, 2019 at 15:55
I found this doc, but If I asked the question here with details, it's I need help to understand what I missed in this information @Pizzalord — shtb2708
– shtb2708, Commented Mar 5, 2019 at 15:59

SubXaero · Accepted Answer · 2019-03-05 16:06:58Z

1

Presuming that the file contains dynamic and unknown keys and values, and you cannot model them in your application. Then you can do something like:


func main() {
    if os.Args[1] == "update-json-from-json" {
        ...
        jsonFile := readInput()

        var jsonKeys interface{}
        err := json.Unmarshal(jsonFile, &jsonKeys)
        functions.Check(err)


        ...
    }
}

to load the contents into the empty interface, and then use the go reflection library (https://golang.org/pkg/reflect/) to iterate over the fields, find their names and values and update them according to your needs.

The alternative is to Unmarshal into a map[string]string, but that won't cope very well with nested JSON, whereas this might (but I haven't tested it).

answered Mar 5, 2019 at 16:06

SubXaero

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