How can I split my koa routes into separate files?

I'm trying to figure out how to split my routes into separate files.

I have this so far, but it doesn't work. I just get Not found when I try to access http://localhost:3001/api/things

//server.js
var koa = require('koa');
var app = koa();
var router = require('koa-router');

app.use(router(app));
require('./routes')(app);


// routes.js
module.exports = function *(app){
  app.use('/api/things', require('./api/things'));
};


// api/things/index.js

var Router = require('koa-router');
var router = new Router({
  prefix: '/api/things'
});

router.get('/', function *(){
  this.body = [{ name: 'Foo'}, { name: 'Bar' }];
});

module.exports = router;

---

EDIT: I've updated the code examples below because the koa-router package on npm is no longer maintained. The Koa team has made an official fork of it under the name @koa/router.

---

For anyone reading this, who is curious on how to do this in Koa 2.X:

app.js

import Koa from 'koa'
import rootRouter from './routes/root'
import userRouter from './routes/user'

const app = new Koa()

app.use(rootRouter.routes())
app.use(rootRouter.allowedMethods())
app.use(userRouter.routes())
app.use(userRouter.allowedMethods())

export default app

routes/root.js

import Router from '@koa/router'
const router = new Router()

router.get('/', async (ctx, next) => {
  ctx.body = 'Hello'
})

export default router

routes/user.js

import Router from '@koa/router'
const router = new Router({ prefix: '/user' })

router.get('/', async (ctx, next) => {
  ctx.body = 'Some User'
})

export default router

If you want to avoid the repetition with the routes() and the allowedMethods(), you can use koa-compose to compose the middleware together. For simplicity, I made a wrapper around it to simplify working with koa-router. Using it would look something like this:

app.js

import Koa from 'koa'
import router from './routes'

const app = new Koa()

app.use(router())

export default app  

routes/index.js

import combineRouters from 'koa-combine-routers'
import rootRouter from './root'
import userRouter from './user'

const router = combineRouters(
  rootRouter,
  userRouter
)

export default router

And it would do the same thing.