title: ExpressJs is return error `ERR_MODULE_NOT_FOUND` if I import the file without `js` extension
body: <p>I build a expressJs app by ES6 and I got the below error:</p>
  
  <pre><code>(node:4132) ExperimentalWarning: The ESM module loader is experimental.
  internal/modules/run_main.js:54
      internalBinding('errors').triggerUncaughtException(
                                ^
  
  Error [ERR_MODULE_NOT_FOUND]: Cannot find module 'E:\wamp64\www\myDemos\nodeJs\expressJsExample\config\app' imported from E:\wamp64\www\myDemos\nodeJs\expressJsExample\server.mjs
  ←[90m    at finalizeResolution (internal/modules/esm/resolve.js:255:11)←[39m
  ←[90m    at moduleResolve (internal/modules/esm/resolve.js:603:10)←[39m
  ←[90m    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:644:13)←[39m
  ←[90m    at Loader.resolve (internal/modules/esm/loader.js:94:40)←[39m
  ←[90m    at Loader.getModuleJob (internal/modules/esm/loader.js:240:28)←[39m
  ←[90m    at ModuleWrap.&lt;anonymous&gt; (internal/modules/esm/module_job.js:42:40)←[39m
  ←[90m    at link (internal/modules/esm/module_job.js:41:36)←[39m {
    code: ←[32m'ERR_MODULE_NOT_FOUND'←[39m
  }
  [nodemon] app crashed - waiting for file changes before starting...
  </code></pre>
  
  <p>If I use <code>import app from './config/app.js';</code> then working but if I use <code>import app from './config/app';</code> then return the above error.</p>
  
  <p>The below is my code:</p>
  
  <p><strong>package.json</strong></p>
  
  <pre><code>{
    "name": "ExpressJsExample",
    "version": "1.0.0",
    "description": "Express Js Example",
    "main": "server.js",
    "type": "module",
    "scripts": {
      "test": "echo \"Error: no test specified\" &amp;&amp; exit 1",
      "start": "nodemon server.js"
    },
    "author": "Mukesh Singh Thakur",
    "license": "ISC",
    "dependencies": {
      "body-parser": "^1.19.0",
      "chalk": "^4.0.0",
      "dotenv": "^8.2.0",
      "express": "^4.17.1",
      "http": "0.0.1-security",
      "http-errors": "^1.7.3",
      "jsonwebtoken": "^8.5.1",
      "nodemon": "^2.0.2",
      "pg": "^8.0.0",
      "request": "^2.88.2",
      "sequelize": "^5.21.6"
    },
    "devDependencies": {
      "sequelize-cli": "^5.5.1"
    }
  }
  </code></pre>
  
  <p><strong>server.js</strong></p>
  
  <pre><code>import http from 'http';
  import app from './config/app';
  
  const server = http.Server(app);
  server.listen(3000, () =&gt; {
         return true;
  });
  </code></pre>
  
  <p><strong>app.js</strong></p>
  
  <pre><code>import express from 'express';
  const app = express();
  
  export default app;
  </code></pre>
  
  <p>The example app is available in <code>https://github.com/msthakur08/express-js-example</code> URL. The example files import with '.js' existence but I want to import file without '.js' existence.</p>