Learning Node and issues with mysql query - mysql

Question

i'm learning node and have hit an issue with running a mysql query. I am certain i am getting connectivity to the mysql db (as when i run the query from the same module as i connect to the DB i am able to print the rows to the console log). However i get a 500 error when i require the DB connection into my another file and use in the query. I've spent last few hours on stack overflow and still stuck. Its definitely not the function as if i just return text it works fine so its definitely something around the way i am utilising the db connection. The DB connection file is below:
// initialize database connection
const mysql = require('mysql')
var db;
function connectDatabase() {
if (!db) {
db = mysql.createConnection({
host: process.env.DB_HOST,
user: process.env.DB_USER,
password: process.env.DB_PASS,
database: process.env.DB_DATABASE
})
db.connect(function(err){
if(!err) {
console.log('Database is connected!')
} else {
console.log('Error connecting database!')
}
})
}
return db
}
module.exports = connectDatabase()
The module where the DB connection us used in query below:
const db = require('../db').connectDatabase
exports.getNightlyRatesData = () => {
//const { rows } = db.query('SELECT * FROM rate', function (err, rows) {
db.query('SELECT * FROM rate', function (err, rows) {
if (err) {
console.log("ERROR");
console.log(err);
return;
}
console.log("good");
})
return rows
}