No environment variables with Next.js TypeScript Custom server

Question

I am currently building a next.js app for a course at uni. I want to run a script when the development server starts that performs some API calls to update the database with new events for the webpage to display. I only want to run this script when the development server starts.

I therefore created a custom server since I thought that would give me the opportunity to call the function in the server file like below:

import next from 'next';
import { NextServer, RequestHandler } from 'next/dist/server/next';
import syncGasque from './lib/gasquesync';

const port = 3000;
const dev = process.env.NODE_ENV !== 'production';
const app : NextServer = next({ dev });
const handle : RequestHandler = app.getRequestHandler();

app.prepare().then(() => {
    const server = express();

    server.all('*', (req : Request, res : Response ) => handle(req, res));

    server.listen(port, () => {
        console.log("Server started at http://localhost:" + port+"/");
    });

    console.log(process.env.NODE_ENV); // Prints dev
    console.log(process.env.MONGODB_URI); // Prints the uri
    console.log(process.env.MONGODB_DB); // Prints the db name
    
    syncGasque();
});

I want to run "syncGasque" which is a script that establishes a connection to the database to perform some insertions and updates (mongodb), and naturally it needs the env variables for the db. The code works when I don't call the function: the server starts and the frontend displays information from the database. When i do include the function like above it does not work and gives me this error message:

/Users/simpen/dev/chalmers/dat257-hasse-andersson/client/lib/mongodb.ts:8
  throw new Error('Please add your Mongo URI to .env.local')
        ^
Error: Please add your Mongo URI to .env.local
    at Object.<anonymous> (/Users/simpen/dev/chalmers/dat257-hasse-andersson/client/lib/mongodb.ts:8:9)
    at Module._compile (node:internal/modules/cjs/loader:1095:14)
    at Module.m._compile (/Users/simpen/dev/chalmers/dat257-hasse-andersson/client/node_modules/ts-node/src/index.ts:1455:23)
    at Module._extensions..js (node:internal/modules/cjs/loader:1147:10)
    at Object.require.extensions.<computed> [as .ts] (/Users/simpen/dev/chalmers/dat257-hasse-andersson/client/node_modules/ts-node/src/index.ts:1458:12)
    at Module.load (node:internal/modules/cjs/loader:975:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:999:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.<anonymous> (/Users/simpen/dev/chalmers/dat257-hasse-andersson/client/lib/db.service.ts:2:1)

Here is the scripts from my package.json file. I am using dev.

"scripts": {
    "dev": "NODE_ENV=development ts-node server.ts",
    "lint": "next lint",
    "build": "next build"
}

This is the mongodb.ts file:

declare global {
  var _mongoClientPromise: Promise<MongoClient>
}

if (!process.env.MONGODB_URI) {
  throw new Error('Please add your Mongo URI to .env.local')
}

const uri: string = process.env.MONGODB_URI
const options = {}

let client: MongoClient
let clientPromise: Promise<MongoClient>


if (process.env.NODE_ENV === 'development') {
  // In development mode, use a global variable so that the value
  // is preserved across module reloads caused by HMR (Hot Module Replacement).
  if (!global._mongoClientPromise) {
    client = new MongoClient(uri, options)
    global._mongoClientPromise = client.connect()
  }
  clientPromise = global._mongoClientPromise
} else {
  // In production mode, it's best to not use a global variable.
  client = new MongoClient(uri, options)
  clientPromise = client.connect()
}

// Export a module-scoped MongoClient promise. By doing this in a
// separate module, the client can be shared across functions.
export default clientPromise

Any ideas as to why this is happening?