things.js

mediator.on("receive:thingsFromDB", function(things) {
  // how I get res here?
  res.send(things);
});

app.get("/things", function(req, res) {
  mediator.emit("request:thingsFromDB");
});

mediator.on("receive:thingsFromDB", function(cb) {
    var things = getFromDb();
    cb(things);
});

app.get('/things', function(req, res) {
    mediator.emit("request:thingsFromDB", function(things) {
        res.send(things);
    });
});