Express style middleware callstack with koa-compose

app.js

'use strict'
const koa = require('koa')
const compose = require('koa-compose')

const app = koa() 

const first = function * (next) {
  console.log('first')
  yield next
}

const second = (foo) => {
  return function * (next) {
    console.log(`second with param ${foo}`)
    yield next
  }
}

const last = function * () {
  this.body = 'Hello world\n'
}

app.use(compose([
  first,
  second('bar'),
  last
]))

app.listen(3000)

The Express equivalent would have been something like:

const express = require('express')
const app = express()

const first = function(req, res, next) {
  console.log('first')
  next()
}

const second = function(foo) {
  return function(req, res, next) {
    console.log(`second with param ${foo}`)
    next()
  }
}

const last = function(req, res) {
  res.send('Hello world\n')
}

app.use([first, second('bar'), last])

app.listen(3000)