使用gmail的Nodemailer，无法在字符串“ SMTP”上创建属性“ mailer”

我试图将数据从创建的表单发送到我的gmail帐户，当单击sumbit按钮时，我总是会遇到相同的错误。我发现了许多有关nodemailer的问题，但似乎没有一个与我遇到的问题相同。

当然，我已经声明了我的clientId，但为此帖子删除了。

TypeError: Cannot create property 'mailer' on string 'SMTP'
at Mail (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\nodemailer\lib\mailer\index.js:45:33)
   at Object.module.exports.createTransport (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\nodemailer\lib\nodemailer.js:46:14)
   at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\src\app.js:39:26
   at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
   at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\route.js:131:13)
   at Route.dispatch (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\route.js:112:3)
   at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
   at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:277:22
   at Function.process_params (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:330:12)
   at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:271:10)
   at serveStatic (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\node_modules\serve-static\index.js:75:16)
   at Layer.handle [as handle_request] (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\layer.js:95:5)
   at trim_prefix (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:312:13)
   at C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:280:7
   at Function.process_params (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:330:12)
   at next (C:\Users\snowr\Documents\dev\zorgkaartnl\zorgkaartnl\node_modules\express\lib\router\index.js:271:10)

这是我的app.js：

// require modules
const express = require('express');
const app = express();
const pug = require('pug');
const fs = require('fs')
const bodyParser = require('body-parser');
const pg = require('pg');
const nodemailer = require('nodemailer');
const xoauth2 = require('xoauth2');


//set view engine and views
app.set('views', 'src/views');
app.set('view engine', 'pug');

app.use(bodyParser.urlencoded({extended: false}));
app.use(express.static('./resources/'));





//display index page
app.get('/', function ( req, res ){
  console.log('Index is displayed on localhost');
    res.render('index');
});

app.post('/zorginstelling/ziekenhuis-olvg-locatie-west-voorheen-sint-lucas-andreas-ziekenhuis-amsterdam-109428/waardeer', function (req, res) {
  var mailOpts, smtpTrans;
  console.log('form word gepost')
  //Setup Nodemailer transport, I chose gmail. 
  smtpTrans = nodemailer.createTransport('SMTP', {
      service: 'Gmail',
      auth: {
        xoauth2: xoauth2.createXOAuth2Generator({
            user: '[email protected]',
            clientId: '-' ,
            clientSecret: '-' ,
            refreshToken: '-'
        })
       }
  });

   //Mail options
  mailOpts = {
      from: req.body.rating[name] + ' <' + req.body.rating[email][first] + '>', 
      to: '[email protected]',
      subject: 'Test',
      text: req.body.rating[comment] + req.body.rating[questions][behandeling] + req.body.rating[name]
  };

    smtpTrans.sendMail(mailOpts, function (error, response) {
      //Email not sent
      if (error) {
          console.log('There was a problem')
      }
      //Yay!! Email sent
      else {
          console.log('Email sent!')
      }
  });
});



var server = app.listen(4000, function () {
        console.log('Example app listening on port: ' + server.address().port);
    });