app.js

const Koa = require('koa');
const Router = require('koa-router');

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

app.use(async (ctx, next) => {
  const { request, response } = ctx;
  const now = Date.now();
  await next();
  console.log(`${request.method} ${request.url} ${response.status} ${response.length} - ${Date.now() - now} ms`);
}); 

router.get('/', async (ctx, next) => {
  ctx.body = { hello: 'world' };
});

app.use(router.routes()).listen(process.env.PORT);

index.js

require('async-to-gen/register');
require('./app');

package.json

{
  "dependencies": {
    "async-to-gen": "^1.1.4",
    "koa": "^2.0.0",
    "koa-router": "^7.0.1"
  }
}