app.coffee

koa = require("koa")
app = koa()

# x-response-time

app.use (next) ->
  start = new Date
  yield next
  ms = new Date - start
  @set 'X-Response-Time', ms + 'ms'

# logger

app.use (next) ->
  start = new Date
  yield next
  ms = new Date - start
  console.log '%s %s - %s', this.method, this.url, ms

# response

app.use (next) ->
  this.body = "Hello World"
  yield next

app.listen(3000)