title: Concurrent in Nodejs
body: <p>I have node server like below. And i push 2 request that 
  almost simultaneously(with the same url = "localhost:8080/").
  And my question is: "Why the server wait for 1st request handle done, then 2st request will be handle"?</p>
  
  <ul>
  <li>Output in console of my test: </li>
  </ul>
  
  <pre>
  Home..
  Home.. 
  </pre>
  
  <p>(Notes: 2nd line will be display after 12second)
  - server.js:</p>
  
  <pre>
  
      var express = require('express')
      var app = express()
      app.use(express.json())
  
      app.get('/', async(request, response) => {
          try {
              console.log('Home ...')
              await sleep(12000)
              response.send('End')
          } catch (error) {
              response.end('Error')
          }
      })
  
  
      function sleep(ms) {
        return new Promise(resolve => setTimeout(resolve, ms));
      }
  
      var server = app.listen(8080, '127.0.0.1', async () => {
          var host = server.address().address
          var port = server.address().port
          console.log('====================  START SERVER  ===================')
          console.log('* Running on http://%s:%s (Press CTRL+C to quit)', host, port)
          console.log('* Create time of ' + new Date() + '\n')
      })
  
  
  </pre>