How do I access res.locals after calling app.router?

I am creating the middleware to be called after app.router and I need to access the data that was stored in res.locals object by the route middleware and route handler.

//...
app.use(app.router);
app.use(myMiddleware);
//...

app.get('/', function(req, res) {
    res.locals.data = 'some data';
});

function myMiddleware(req, res, next) {
    if (res.locals.data)
        console.log('there is data');
    else
        console.log('data is removed'); // that's what happens
}

The problem is that all properties of res.locals become empty after app.router.

I tried to find the place where express or connect cleans res.locals to somehow patch it but so far I can't find it.

The only solution I see at the moment is to abandon the idea of putting this logic in a separate middleware and put it in route-specific middleware, where res.locals is available, but it will make the system much more interconnected. Also I have many routes where route middleware does not call next (when res.redirect is called), so I will have to do many changes to make it work. I'd very much like to avoid it and put this logic in a separate middleware, but I need to access the data that was stored in res.locals.

Any help really appreciated.

You can possibly bind it before, but have it act after. The logger middleware is an example of this.

app.use(express.logger('tiny'));
app.use(myMiddleware);
app.use(app.router);

function myMiddleware(req, res, next) {
    var end = res.end;
    res.end = function (chunk, encoding) {
        res.end = end;
        res.end(chunk, encoding);

        if (res.locals.data)
            console.log('there is data');
        else
            console.log('data is removed');
    };

    next();
}

app.get('/', function (req, res) {
    res.locals.data = 'some data';
    res.send('foo'); // calls `res.end()`
});

Requesting / results in:

GET / 200 3 - 6 ms
there is data
GET /favicon.ico 404 - - 1 ms
data is removed