Koa.js - serving static files and REST API

I'm new to koa.js library and I need some help. I'm trying to make simple REST application using koa. I have a static html and javascript files I want to serve on route / and REST API accessing from /api/.

This is my project directory tree:

project
├── server
│   ├── node_modules
│   ├── package.json
│   └── src
│       ├── config
│       ├── resources
│       └── server.js
├── ui
│   ├── app
│   ├── bower.json
│   ├── bower_components
│   ├── dist
│   ├── node_modules
│   ├── package.json
│   └── test

This is my source:

var app = require('koa')();
app.use(mount('/api/places', require('../resources/places')));

// does not work
var staticKoa = require('koa')();
staticKoa.use(function *(next){
  yield next;
  app.use(require('koa-static')('../ui/app', {}));
});
app.use(mount('/', staticKoa));

// does not work
app.use(mount('/', function*() {
    app.use(require('koa-static')('../ui/app/', {}));
}));

// does not work
app.use(mount('/', function*() {
    app.use(require('koa-static')('.', {}));
}));
// GET package.json -> 404 not found

I've tried koa-static, koa-static-folder, koa-static-server libraries and neither works so I'm doing something wrong.

I've tried this and it works, but I don't have access to my REST api:

var app = require('koa')();
app.use(require('koa-static')('../ui/app/', {}));

It was a little hard for me to follow what you were doing in your example code... Here is a simple example that does everything your wanting:

'use strict';
let koa     = require('koa'),
    send    = require('koa-send'),
    router  = require('koa-router')(),
    serve   = require('koa-static');

let app = koa();
// serve files in public folder (css, js etc)
app.use(serve(__dirname + '/public'));

// rest endpoints
router.get('/api/whatever', function *(){
  this.body = 'hi from get';
});
router.post('/api/whatever', function *(){
  this.body = 'hi from post'
});

app.use(router.routes());

// this last middleware catches any request that isn't handled by
// koa-static or koa-router, ie your index.html in your example
app.use(function* index() {
  yield send(this, __dirname + '/index.html');
});

app.listen(4000);