Google Auth with Node.js JWT

jwt.js

const fetch = require('node-fetch');
const FormData = require('form-data');
const JSONWebToken = require('jsonwebtoken');

const getAuthToken = async function (args){
    args.duration = args.duration || 60;
    args.scope = args.scope instanceof Array? args.scope.join(' ') : args.scope;
    let form = new FormData();
    form.append('grant_type', 'urn:ietf:params:oauth:grant-type:jwt-bearer');
    form.append('scope', args.scope);
    form.append('assertion', JSONWebToken.sign(
        {
            iss : args.service_account_id,
            scope : args.scope,
            aud : 'https://accounts.google.com/o/oauth2/token'
        },
        args.private_key,
        {
            algorithm: 'RS256',
            expiresIn: '1h'
        }
    ));

    let res = await fetch('https://accounts.google.com/o/oauth2/token', {
        method: 'POST',
        body: form
    });
    let json = await res.json();
    console.log(json);
    return 'Bearer ' + json.access_token;
}

const eg = async function () {
    let  authorization = await getAuthToken({
        service_account_id : SERVICE_AC_ID,
        private_key : PRIVATE_KEY,
        scope : [
            'https://www.googleapis.com/auth/plus.login',
            'https://www.googleapis.com/auth/fusiontables',
            'https://www.googleapis.com/auth/drive',
        ]
    });

    let apiResponse = await fetch(
        'https://www.googleapis.com/fusiontables/v2/tables',
        {
            headers: { authorization }
        }
    );

    let json = await apiResponse.json();
    console.log(json);
    return json;
};

eg();