Express, Handlebars show flash messages

Question

I use Node with express and handlebars. I have a login form and the user should receive a login error message. My code is as follows: Verification (using passport):

...
else if (password != user.password) {
            return done(null, false, req.flash('message', 'Wrong password'));
...

In the routes, I got this:

app.post('/sign-in', passport.authenticate('local', {
        successRedirect : '/', // redirect to the home page
        failureRedirect : '/sign-in', // redirect back to the signup page if there is an error
        failureFlash : true // allow flash messages
    }));

Then, to display my handlebars template,

app.get('/sign-in', function(req, res) {
        res.render("signin.handlebars", {layout: 'users.handlebars', action: 'Sign in', message: req.flash('message'),
                    csrf: 'CSRF token goes here' });
    })

The problem is that the flash message does not appear if necessary when entering the wrong password.

Edit: My express installation:

app.engine('handlebars', handlebars.engine);
app.set('view engine', 'handlebars');
app.set('models', __dirname + '/models');
app.use(express.static(__dirname + '/public'));     // set the static files location /public/img will be /img for users
app.use(cookieParser());
app.use(expressSession({secret:'somesecrettokenhere', resave: true, 
                        saveUninitialized: true, }));
app.use(passport.initialize());
app.use(passport.session());
//app.use(session({ store: new RedisStore }));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
    extended: true
}));
app.use(flash());
app.use(morgan("dev"));
app.disable('x-powered-by');
app.use(function(err, req, res, next) {
    res.status(err.status || 500);
});

Answer 1

I solved it like this: ...

if (!user) {
            return done(null, false, {
                message: 'The email you entered is incorrect'
            });

... This encodes the message in JSON. Then on the routes I got:

app.get('/sign-in', function(req, res) {
        res.render("signin.handlebars", {layout: 'users.handlebars', action: 'Sign in', ***error: req.flash('error')***,
                    csrf: 'CSRF token goes here' });
    })

Then in my handlebars template:

{{#if error}}
    <div class="alert alert-danger">{{error}}</div>
{{/if}}