ctx.render is not a function
```
// dependencies
import Koa from 'koa';
import jade from 'jade';
import path from 'path';

// middleware dependencies
import Router from 'koa-router';
import views from 'koa-views';
import convert from 'koa-convert';

// init
const app = new Koa();
const router = new Router();

// middlewares
app.use(convert(views(__dirname + '/views', { extension: 'jade' })));
app.use(convert(router.routes())).use(convert(router.allowedMethods()));

// routes
router.get('/', async function (ctx, next) {
  await ctx.render('index');
});

// start app
app.listen(8080);
export default app;
```

What's wrong with this code? I tried different versions, but always get TypeError...
