koa.js

var koa = require('koa');
var app = koa();
var Promise = require('promise');

var sleep = function(n) {
  return new Promise(function(accept) {
    setTimeout(accept, n);
  });
};

function* yetAnother() {
  var now = Date.now();
  yield sleep(2000);
  console.log('awaiting....', Date.now() - now);
  yield sleep(100);
  console.log('holy fucks this is nice', Date.now() - now);
}

function* otherGen (value) {
  console.log(value);
  yield sleep(100);
  console.log('100ms')
  yield sleep(2000);
  console.log('2000ms')
  yield yetAnother();
}

app.use(function *() {
  yield otherGen('is a thing');
  console.log('http woot');
  this.body = 'http woot';
});

app.listen(3000);