$ npm install koa-logger

const logger = require('koa-logger')
const Koa = require('koa')
const app = new Koa()
app.use(logger())

const logger = require('koa-logger')
const Koa = require('koa')
const app = new Koa()
app.use(logger((str, args) => {
  // redirect koa logger to other output pipe
  // default is process.stdout(by console.log function)
}))

app.use(logger({
  transporter: (str, args) => {
    // ...
  }
}))