connect-flash和jade:无法显示flash flashahe

我现在开始使用Express,并希望显示一条简单的flash错误消息,这只是无法正常工作.

app.js

var flash = require('connect-flash');
...

var app = express(); // create an express app

// configure environments
app.configure(function(){
    ...
    app.use(express.cookieParser('keyboard cat'));
    app.use(express.session({ cookie: { maxAge: 60000 }}));
    app.use(flash());
    app.use(app.router);
});

app.get('/signup', routes.signup);
app.post('/signup', routes.adduser);
...

和我的 router.js

exports.signup = function(req, res) {
    console.log(req.flash('error'));
    res.render('signup', {message: req.flash('error')});
}

和

exports.adduser = function(req, res) {

    // get the form values from "name" attribute
    var username = req.body.username;
    var email = req.body.useremail;
    var password = req.body.userpassword;

    User.findOne({'username': username}, function(err, user) {
        if (user) {
            console.log('user exists');
            req.flash('error', 'Username exists');
            res.redirect('/signup');
        } else {
            ...
            ...

现在,我想要的是,如果用户存在,重定向回signup闪烁错误/信息/任何消息.

我的玉模板signup.jade是

extends ../layouts/default

block content
    h1 Sign Up

    if message && message.length
        strong #{message}

    form#formAddUser(name="adduser", method="post", action="/signup")
        input#inputUserName(type="text", placeholder="username", name="username")
        input#inputPassword(type="password", placeholder="password", name="userpassword")
        input#inputUserEmail(type="text", placeholder="email", name="useremail")
        button#btnSubmit(type="submit") Sign Up

这不会显示任何错误.我也试过for看,索引访问等但没有任何作用.我究竟做错了什么？我该如何解决？