Error in Express routing?

Question

Node.js

I'm trying to make a simple server on node.js (4.2.6) + express (4.14.0)
Which, in response to a request with the version parameter, returns the value of this parameter.
If you open the url " localhost:8080/api/v10 ", for some reason in I get an error: "Cannot GET /api/v10"
What am I doing wrong?

var express         = require('express');
var path            = require('path');
var bodyParser      = require('body-parser');

var app = express();

app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json());

var router = express.Router();

router.get('/api:version', function (req, res) {
    res.send(req.params.version);
});

app.use('/', router);

var listener = app.listen(8080, function(){
    console.log('******* Express server listening on port ' + listener.address().port);
});

Answer 1

app.get('/user/:id'