problem with routes with node-oidc-provider

Question

I'm just starting with oidc-provider and I can't get express to recognize routes once I include oidc-provider.

In the simple setup below, I get a "unrecognized route on '/'. The well known url for setup does work, and the auth endpoint looks like it does as well.

const express = require('express');
const Provider = require('oidc-provider').Provider;

const app = express();

const configuration = {
  // ... see /docs for available configuration
  clients: [{
    client_id: 'foo',
    client_secret: 'bar',
    redirect_uris: ['http://192.168.128.128:3000/oidc/cb'],
    // ... other client properties
  }],
};

const oidc = new Provider('http://localhost:3000', configuration);

app.use('/oidc', oidc.callback());

app.get('/', function(req, res) {
        res.send('hello world');
});

oidc.listen(3000, () => {
  console.log('oidc-provider listening on port 3000, check http://localhost:3000/.well-known/openid-configuration');
});

I don't understand the whole "mount" notion though I suspect it has something to do with my route problem. Why is this happening? What is the solution?