Error in Usage example

[HeyJ0e]

The Usage section tells:

polka()
  .use(one, two)
  .get('/users/:id', (req, res) => {
    console.log(`~> Hello, ${req.hello}`);
    res.end(`User: ${req.params.id}`);
  })
  .listen(3000, err => {
    if (err) throw err;
    console.log(`> Running on localhost:3000`);
  });

Where the listen provides a handler which expects err.

.listen(3000, err => {

The thing is, err will be always undefined as listening event provides nothing.
listening event documentation: https://nodejs.org/api/net.html#net_event_listening