Koa hello world example with response time middleware

index.js

'use strict'

const Koa = require('koa')
const app = new Koa()

app.use(async (context, next) => {
  let start = Date.now()
  await next()
  let ms = Date.now() - start
  context.set('X-Response-Time', ms + 'ms')
  console.log(context.method + ' ' + context.url + ' - ' + ms + 'ms')
})

app.use(async context => {
  context.body = 'Hello, World!'
})

app.listen(3000)