Async .mjs works when calling directly, fails when called from another .mjs - node.js

Question

I am currently working with the Ring-Client-API and am running into a small issue at the very end of my development. I succesfully created, tested, and ran my RingListener as an individual file, ie by executing RingListener.mjs. My goal is to now start the listener from another file location, and I am running into some issues trying to do that. I am more familiar with CommonJS so please feel free to point me in the right direction for ES6 stuff I am missing. I am running node 14.15.4
Code RingListener.mjs:
import {RingApi} from 'ring-client-api'
import * as dotenv from "dotenv";
dotenv.config({path: '../.env'});
import {readFile, writeFile} from 'fs'
import {promisify} from 'util'
import App from "../objects/GoogleHomeNotification.js";
export async function start() {
const {env} = process;
console.log("Test 1")
const ringApi = new RingApi({my credentials});
console.log("Test 2")
const allCameras = await ringApi.getCameras();
console.log("Test 3")
console.log("Found " + allCameras.length + " camera(s)")
ringApi.onRefreshTokenUpdated.subscribe(
async ({newRefreshToken, oldRefreshToken}) => {
console.log('Refresh Token Updated: ', newRefreshToken)
}
)
if (allCameras.length) {
console.log('Listening for motion and doorbell presses on your cameras.')
}
}
start();
Output for RingListener.mjs
Test 1
Test 2
Test 3
Found 1 camera(s).
Refresh Token Updated: {my token}
Now writing it to proper .env file
Listening for motion and doorbell presses on your cameras.
When I try to start it from my other file, I only reach Test 2.
Start.mjs
import {start} from './objects/RingListener.mjs'
start();
//await start(); //Returns the same results as just start()
Output for Start.mjs
Test 1
Test 2
When running it from another location it seems to get stuck at the first await statement, and I'm not sure why. Any help would be greatly appreciated. I am quite stumped because I am able to actually execute the function and I get the console log statements, but for some reason it keeps failing at the exact same spot with the await call when executed through another file. Is there something I am missing when calling an async function from another file?
Thank you!
EDIT: Thanks #JoshA for pointing me in the right direction for the filepath for dotenv.
The following code now hangs on the "Test 1 Test 2" when I try to import another js module.
import {start} from './objects/RingListener.mjs'
import {default as Webserver} from './app.js'
await start();
Output
Test 1
Test 2
But when I remove my import to the other class it runs perfectly, IE "Test 1, 2, 3, etc".
import {start} from './objects/RingListener.mjs'
//import {default as Webserver} from './app.js'
await start();
Output
Test 1
Test 2
Test 3
Found 1 camera(s).
Refresh Token Updated:
Now writing it to proper .env file
Listening for motion and doorbell presses on your cameras.
I'm not even using it yet and it still is causing it to hang. Eventually I am going to use Webserver.listen(); but the ./app.js just exports the express app.
EDIT: The app.js contains a bunch of variable initialization and express app configuration. Mapping to the different routes on the server. The goal is to remove the app.listen() in the app.js and move it to the Start.mjs and call it by Webserver.listen() from the import.
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var logger = require('morgan');
require('dotenv').config()
/* Variable def here */
var app = express();
// app config here
/* Exports */
module.exports = app;
app.listen(1337, () => {
console.log("Starting server on 1337");
})

Answer 1

I assume you are using dotenv to load your credentials from your .env file which you then pass on to the new RingApi({my credentials}) constructor.
If that's the case, the most likely reason it's failing is that dotenv uses fs.readFileSync to read the .env file which looks for files relative to the path where node js was executed and not relative to the path of the module. Which is why it stops working if you execute the app from the Start.mjs which is in a different path.
If you really want to keep the dotenv config call inside your RingListener.mjs file you can rewrite it to something like this which resolves the absolute path for the .env file.
import { resolve } from 'path';
dotenv.config({path: resolve(__dirname, '../.env')});
If you get an error __dirname is not defined this is because it's not available in ECMAScript modules as documented here.
As a workaround, you can do something like this.
import { fileURLToPath } from 'url';
import { dirname, resolve } from 'path';
// Initialize __dirname
const __dirname = dirname(fileURLToPath(import.meta.url));
// Then use it to resolve path for .env
dotenv.config({path: resolve(__dirname, '../.env')});