text: #!/usr/bin/env node
  
  /**
   * Module dependencies.
   */
  var Koa = require('koa2')
  var app = new Koa()
  var views = require('koa-views')
  var json = require('koa-json')
  var onerror = require('koa-onerror')
  var bodyparser = require('koa-bodyparser')
  var logger = require('koa-logger')
  
  var index = require('./routes/index')
  
  // error handler
  onerror(app)
  
  // middlewares
  app.use(bodyparser({
    enableTypes: ['json', 'form', 'text']
  }))
  app.use(json())
  app.use(logger())
  app.use(require('koa-static')(__dirname + '/views'))
  
  app.use(views(__dirname + '/views/html', {
    extension: 'html'
  }))
  
  // logger
  app.use(async (ctx, next) => {
    var start = new Date()
    await next()
    var ms = new Date() - start
    console.log(`${ctx.method} ${ctx.url} - ${ms}ms`)
  })
  
  // routes
  app.use(index.routes(), index.allowedMethods())
  
  var debug = require('debug')('demo:server');
  var http = require('http');
  
  /**
   * Get port from environment and store in Express.
   */
  
  var port = normalizePort(process.env.PORT || '3000');
  // app.set('port', port);
  
  /**
   * Create HTTP server.
   */
  
  var server = http.createServer(app.callback());
  
  /**
   * Listen on provided port, on all network interfaces.
   */
  
  server.listen(port);
  server.on('error', onError);
  server.on('listening', onListening);
  
  /**
   * Normalize a port into a number, string, or false.
   */
  
  function normalizePort(val) {
    var port = parseInt(val, 10);
  
    if (isNaN(port)) {
      // named pipe
      return val;
    }
  
    if (port >= 0) {
      // port number
      return port;
    }
  
    return false;
  }
  
  /**
   * Event listener for HTTP server "error" event.
   */
  
  function onError(error) {
    if (error.syscall !== 'listen') {
      throw error;
    }
  
    var bind = typeof port === 'string'
      ? 'Pipe ' + port
      : 'Port ' + port;
  
    // handle specific listen errors with friendly messages
    switch (error.code) {
      case 'EACCES':
        console.error(bind + ' requires elevated privileges');
        process.exit(1);
        break;
      case 'EADDRINUSE':
        console.error(bind + ' is already in use');
        process.exit(1);
        break;
      default:
        throw error;
    }
  }
  
  /**
   * Event listener for HTTP server "listening" event.
   */
  
  function onListening() {
    var addr = server.address();
    var bind = typeof addr === 'string'
      ? 'pipe ' + addr
      : 'port ' + addr.port;
    debug('Listening on ' + bind);
  }
  