NodeJS app to access Google Cloud Identity Aware Proxy

app.js

const request = require('request');
const log4js = require("log4js");
const jwt = require('jsonwebtoken');

const logger = log4js.getLogger();

const secure_IAAP_URL = 'https://YOUR_PROTECTED_PAGE';

const iap_clientID = 'client_id_for_iaap.apps.googleusercontent.com';
const svc_account = "service_account_for_json_cert_file.iam.gserviceaccount.com";
const projectId = 'your_project_id';

const cert = '/path/to/your/cert/file.json';

    var client = require(cert);
    private_key = client.private_key;

    jwt_payload = {
      "iss": svc_account,
      "aud": "https://www.googleapis.com/oauth2/v4/token",
      "exp":  Math.floor(Date.now() / 1000) + (60),
      "iat":  Math.floor(Date.now() / 1000),
      "target_audience": iap_clientID
    }

    var signedJwt = jwt.sign(jwt_payload, private_key, { algorithm: 'RS256' });
    logger.info('Signed JWT: ' + signedJwt);
    request.post('https://www.googleapis.com/oauth2/v4/token', {
      form: {
         'grant_type':'urn:ietf:params:oauth:grant-type:jwt-bearer',
         'assertion' : signedJwt
       }
     }, function (err, response, body) {
       if (err) {
         throw err;
       }
       id_token = JSON.parse(body).id_token;
       logger.info("Acquired Google IDToken: " + id_token);

       logger.info("Making IAAP request to endpoint: " + secure_IAAP_URL);
       var options = {
         url: secure_IAAP_URL,
         headers: {
           'Authorization': 'Bearer ' + id_token
         }
       };
       request(options,function (error, response, body) {
         if (err) {
            throw err;
         }
         logger.info('statusCode:', response && response.statusCode);
         logger.info(body)
       });

     }
   );