Express app won't connect to docker postgres instance in production - postgresql

Question

I am building a webapp using express and postgres. For building my app I use the following files:
docker-compose.yml:
version: '3'
services:
postgres:
image: postgres:12
volumes:
- postgres-volume:/var/lib/postgresql/data
environment:
- POSTGRES_PASSWORD=${ADMIN_DB_PASSWORD}
networks:
- db
restart: unless-stopped
api:
build:
context: ./backEnd/
dockerfile: Dockerfile.debug
volumes:
- ./backEnd/index.js:/app/index.js
ports:
- "80:3002"
networks:
- db
depends_on:
- postgres
environment:
- DB_HOST=postgres
- DB_PORT=5432
- DB_DATABASE=hive
- DB_USER=${DB_API_USER}
- DB_PASSWORD=${DB_API_PASSWORD}
restart: unless-stopped
networks:
db:
The container runs the following code:
const express = require('express');
const bodyParser = require('body-parser')
const pgp = require('pg-promise')();
const connection = {
host: process.env.DB_HOST,
port: process.env.DB_PORT,
database: process.env.DB_DATABASE,
user: process.env.DB_USER,
password: process.env.DB_PASSWORD,
max: 30,
}
const db = pgp(connection);
function getUser(email){
return(
db.oneOrNone("SELECT * FROM users WHERE email = ${email}", {
email:email.toLowerCase()
})
)
}
const app = express();
app.use(bodyParser.json());
app.post('/login', async (req, res)=>{
const email = req.body.email;
console.log(email)
const user = await getUser(email);
console.log("made it past")
});
app.listen(3002, function () {
console.log('Listening on port 3002!');
});
When I call the login endpoint, it faithfully logs the email, but never gets past the
await getUser(email)
It does not throw and error or returns null, it just stays there. Interestingly it is working on my local machine and gets past the await, just not on my linux box.
I have also noticed, that if I change the db host to something nonsensical, pg-promise throws an error on my local machine. It does not however throw an error on my remote linux machine.
Also, if I run the script on the Linux box, without docker, it seamlessly connects to postgres. It appears to be something that only happens in conjunction with docker on Linux.
I am completely stumped by this error, as I have no indication of what is going wrong. The database also appears to be set up correctly, as I can connect to it and use it from my local machine with the same code.
Thank you in advance for your help.