Retrieving Access Token using Service Account by Google's OAuth2 package for Golang

GoTips
golang / Service Account  / accesstoken

Gists

This is a sample golang script for retrieving access token using Service Account of Google by Google’s OAuth2 package.

The script without using Google’s OAuth2 package is here.

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "os"

    "golang.org/x/oauth2"
    "golang.org/x/oauth2/google"
    "golang.org/x/oauth2/jwt"
)

func serviceAccount(credentialFile string) (*oauth2.Token, error) {
    b, err := ioutil.ReadFile(credentialFile)
    if err != nil {
        return nil, err
    }
    var c = struct {
        Email      string `json:"client_email"`
        PrivateKey string `json:"private_key"`
    }{}
    json.Unmarshal(b, &c)
    config := &jwt.Config{
        Email:      c.Email,
        PrivateKey: []byte(c.PrivateKey),
        Scopes: []string{
            "https://www.googleapis.com/auth/drive.metadata.readonly",
        },
        TokenURL: google.JWTTokenURL,
    }
    token, err := config.TokenSource(oauth2.NoContext).Token()
    if err != nil {
        return nil, err
    }
    return token, nil
}

func main() {
    token, err := serviceAccount("credentials.json") // Please set here
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
    fmt.Println(res)
}

 Share!