title: Error [ERR_STREAM_WRITE_AFTER_END]: write after end
body: <p>Code explanation:  I am returning specific HTML file when user visit specific url:   </p>
  
  <pre><code>const http = require('http');
  const fs = require('fs');
  
  fs.readFile('./funkcionalnosti-streznika.html', function(err1, html1) {
      fs.readFile('./posebnosti.html', function(err2, html2) {
          if (err1 || err2) {
              throw new Error();
          }
  
          http.createServer(function(req, res) {
              if (req.url == '/funkcionalnosti-streznika') {
                  res.write(html1);
                  res.end();
              }
              if (req.url == '/posebnosti') {
                  res.write(html2)
                  res.end();
              } else {
                  res.write('random');
                  res.end();
              }
          }).listen(8080)
      })
  });
  </code></pre>
  
  <p>on terminal I've got this error when I visit localhost:8080/funkcionalnosti-streznika:</p>
  
  <pre><code>events.js:288
        throw er; // Unhandled 'error' event
        ^
  
  Error [ERR_STREAM_WRITE_AFTER_END]: write after end
      at write_ (_http_outgoing.js:637:17)
      at ServerResponse.write (_http_outgoing.js:629:15)
      at Server.&lt;anonymous&gt; (/*filelocation*/:19:21)
      at Server.emit (events.js:311:20)
      at parserOnIncoming (_http_server.js:784:12)
      at HTTPParser.parserOnHeadersComplete (_http_common.js:119:17)
  Emitted 'error' event on ServerResponse instance at:
      at writeAfterEndNT (_http_outgoing.js:692:7)
      at processTicksAndRejections (internal/process/task_queues.js:85:21) {
    code: 'ERR_STREAM_WRITE_AFTER_END'
  </code></pre>
  
  <p>I think there is I problem when I close the response too early. How should I change this to be async?.</p>