nodejs flash message disappears from request - node.js

Question

I am trying to post a flash message after authenticating but for some reason the req.flash() loses its value after a redirect.
The code starts when the user asks for a GET on '/'. Here's the code:
const express = require('express');
const session = require('express-session');
const cookie = require('cookie');
const methodOverride = require('method-override')
const passport = require('passport');
const localStrategy = require ('passport-local').Strategy;
const bcrypt = require('bcryptjs');
const cookieParser = require('cookie-parser');
const flash = require('express-flash');
const fs = require('fs');
const config = require('./config.js');
const db = require('./db.js');
const log = require('./logger.js');
const crypto = require('crypto');
var app = express();
const server = require('http').createServer(app);
const build_version = fs.readFileSync("minorBuild.txt").toString();
process.on('UnhandledPromiseRejectionWarning', function(err) {
log.error({ section: "UnhandledPromiseRejectionWarningr", err: err, uid: '1', orgId: '1' });
});
app.set('port', 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'ejs');
app.use(cookieParser(config.cookieSecret));
app.use(flash());
app.use(express.urlencoded({extended: false}));
app.use(express.json());
app.use(session({ name: 'sid',
secret: config.sessionSecret,
cookie: { maxAge: config.sessionCookieMaxAge, domain: 'localhost:3000' },
resave: true,
saveUninitialized: true
}));
app.use(passport.initialize());
app.use(passport.session());
app.use(express.static('public'));
app.use(methodOverride('_method'))
app.get('/', function(req, res, next) {
if (req.isAuthenticated()) {
res.redirect('/dashboard');
} else {
res.render('index', { messages: req.flash("error") });
})
}
});
Once the user POSTS username and password, the data is sent to this function:
app.post('/login', function(req, res, next){
passport.authenticate('local', function(err, user, info){
var redirectUrl = '/';
if (!user) {
req.flash('error', info.messages);
return res.redirect('/');
}
if (req.session.redirectUrl) {
redirectUrl = req.session.redirectUrl;
req.session.redirectUrl = null;
}
req.logIn(user, function(err){
if (err) {
return next(err);
}
});
res.redirect(redirectUrl);
})(req, res, next);
});
The data is authenticated here and the message is set on incorrect auth:
async function authenticateUser (email, password, done) {
await db.getParticipantByEmail(email)
.then(async (getEmailResult) => {
if (getEmailResult === undefined) {
return done(null, false, { messages: "Incorrect Username and/or Password" });
}
});
}
Using the debugger I see the message come back to /login in the info.messages. In this line in the '/login' function:
if (!user) {
req.flash('error', info.messages); //I see the message show up here
return res.redirect('/');
}
After the redirect to '/' req.flash('error') is empty.
res.render('index', { messages: req.flash("error") }); //req.flash("error") is empty here
I have no idea why this is. What am I missing?