old_contents: const Router = require('koa-router')
  const router = new Router()
  const api = new Router()
  
  const users = require('./users-router')
  const articles = require('./articles-router')
  const profiles = require('./profiles-router')
  const tags = require('./tags-router')
  
  api.use(users)
  api.use(articles)
  api.use(profiles)
  api.use(tags)
  
  router.use('/', api.routes())
  
  module.exports = router
  
new_contents: const Router = require('koa-router')
  const router = new Router()
  const api = new Router()
  
  const users = require('./users-router')
  const articles = require('./articles-router')
  const profiles = require('./profiles-router')
  const tags = require('./tags-router')
  
  api.use(users)
  api.use(articles)
  api.use(profiles)
  api.use(tags)
  
  router.use(api.routes())
  
  module.exports = router
  
subject: Fix api route