MRE for https://stackoverflow.com/q/71808396/3001761

.env

FOO=123
BAR=hello, world!

index.js

import "dotenv/config";

function main() {
	const foo = process.env.FOO;
	const bar = process.env.BAR;
	if (!foo || !bar) {
		throw new Error("missing FOO and/or BAR");
	}
	console.log("foo", foo, "bar", bar);
}

main();

package.json

{
  "name": "dotenv-es6",
  "version": "0.1.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "start": "node index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "Jonathan Sharpe <mail@jonrshar.pe>",
  "license": "ISC",
  "dependencies": {
    "dotenv": "^16.0.0"
  }
}
  

session.sh

$ node -v
v16.14.2
$ npm -v
8.5.0
$ npm start

> dotenv-es6@0.1.0 start
> node index.js

foo 123 bar hello, world!