Directly hitting page url in browser only showing index page while serving "next export" out directory

[amalan-shenll]

Bug report

Describe the bug

In exported nextjs application when trying to copy and paste the url "localhost:3000/about" directly in browser only shows the home page only(index.js content only).

To Reproduce

Steps to reproduce the behavior:

1. Create a sample application using "npm init next-app".
2. Create a page name "about.js" under pages directory.
3. Then do "npm run dev" which will run the application in development mode.
4. Now open browser and type or paste "localhost:3000" it will show home page.
5. Then type or paste "localhost:3000/about" it will show about page. (which works fine in dev mode).
6. Now try build and export the application using "npm run build" and then "npm run export".
   Note: "npm run export" should trigger "next export".
7. Above steps will generate "out" directory with static files of application.
8. Now run exported application by "serve -s out" which will run the in "localhost:5000".
9. Now try type or paste "localhost:5000/about" and hit enter. which will show home page instead of about page.

Expected behavior

When pasting "localhost:5000/about" should display about page content not home page content.

System information

• OS: [e.g. Debian 10]
• Browser (if applies) [e.g. chrome, firefox]
• Version of Next.js: [e.g. 9.4.0]
• Version of Node.js: [e.g. 10.18.1]