问Nodejs OAuth错误

EN

var fs = require('fs');
var readline = require('readline');
var google = require('googleapis');
var express = require('express');
var app = express();

var port = 3000;

var OAuth2 = google.auth.OAuth2;
var oauth2client;



app.get('/', function(req, res){

    fs.readFile('client_secret.json', function processClientSecrets(err, content) {
        if (err) {
            console.log('Error loading client secret file: ' + err);
            return;
        }
        // Authorize a client with the loaded credentials, then call the
        // Gmail API.
        var credentials = JSON.parse(content);
        var clientSecret = credentials.web.client_secret;
        var clientId = credentials.web.client_id;
        var redirectUrl = credentials.web.redirect_uris;

        oauth2client = new OAuth2(  
            clientId,
            clientSecret,
            redirectUrl
        );

        var SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];

        var info = "Accedi a GMail"

        var getCode = oauth2client.generateAuthUrl({
            // 'online' (default) or 'offline' (gets refresh_token) 
            access_type: 'offline',

            // If you only need one scope you can pass it as string 
            scope: SCOPES
        });

        res.send(info+"<br><br><button onclick='window.location.href=\""+ getCode +"\"'>Log in</button>");

    });
});


app.get("/code", function(req,res){
    var code = req.query.code;
    res.send(code);
    oauth2client.getToken(code, function (err, tokens) {
    // Now tokens contains an access_token and an optional refresh_token. Save them. 
        if (!err) {
            oauth2Client.setCredentials(tokens);
            console.log(tokens);
        }
        else{
            console.log(err);
        }
    });
});

console.log('Server listen in port '+port+'. Connect to localhost');
app.listen(port);

{ Error: invalid_request
at Request._callback (C:\Users\Edoardo\node_modules\google-auth-library\lib\
transporters.js:81:15)
at Request.self.callback (C:\Users\Edoardo\node_modules\google-auth-library\
node_modules\request\request.js:187:22)
at emitTwo (events.js:106:13)
at Request.emit (events.js:191:7)
at Request.<anonymous> (C:\Users\Edoardo\node_modules\google-auth-library\no
de_modules\request\request.js:1044:10)
at emitOne (events.js:96:13)
at Request.emit (events.js:188:7)
at IncomingMessage.<anonymous> (C:\Users\Edoardo\node_modules\google-auth-li
brary\node_modules\request\request.js:965:12)
at emitNone (events.js:91:20)
at IncomingMessage.emit (events.js:185:7) code: 400 }