Koa 2 examples (with current Koa API)
Thank you for all the great examples! I had to make some modification to get with `"koa": "^2.5.0"`.

I would be happy to add something like this as an additional example if it would be helpful:

(I also left comments on what I had to change)

```javascript
const Koa = require('koa');

const session = require('koa-session');
const Router = require('koa-router'); // New style of router
const mount = require('koa-mount');
const accesslog = require('koa-accesslog');

const Grant = require('grant-koa');
const grant = new Grant(require('./config.json'));

const app = new Koa(); // Must use new keyword
const router = new Router(); // New version of the router

require('koa-qs')(app); // This must happen via require instead of middleware

app.use(accesslog());

// REQUIRED:
app.keys = ['grant'];
app.use(session(app));
// mount grant
app.use(mount(grant));

// Updated to use `ctx` instead of `this`
router.get('/handle_github_callback', async (ctx, next) => {
  console.log(ctx.query);
  ctx.body = JSON.stringify(ctx.query, null, 2);
});

// For the new router
app.use(router.routes()).use(router.allowedMethods());

app.listen(5001, () => {
  console.log('Koa server listening on port ' + 5001);
});
```


