how to use nodejs es6 modules?

I follow the instruction in https://docs.serv00.com/Node.js/#preparing-the-nodejs-application but I want to use es6 modules, I try to change app.js to app.mjs but not working. it shows:

Error 403
Access forbidden
You don't have permission to access the requested object. It is either read-protected or not readable by the server.

You don't have permission to access the requested directory. There is either no index document or the directory is read-protected.

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Please help

chaowenguo Passenger does not support the module. I recommend trying the following solution:

Create a file named index.mjs with the contents of your current app.js.

Replace the contents of app.js with the following line:

import("./app.mjs");
Restart the application.

A 403 error indicates that you likely did not place the startup file in the public_nodejs directory.

Alternatively, you can run the application on a reserved port, for example using pm2, and set up a proxy page.

@admin any idea how to use es6 modules in nodejs？