I'm learning how to use asnyc in Node. Why doesn't my code return anything (logs, errors) to console?

Question

I have the following code which I'm using to learn how to transition from callbacks, through to async, then moving onto promises and finally await.

For the first time, I'm really struggling to understand why I get nothing at all returned to the console.

I have several logging events in place, but these never trigger inside the code, and non of the errors are thrown / exceptions raised.

I have put in additional logging outside the functions to demonstrate that the files running when requesting eg, nodemon app.js from the terminal. However, the terminal hangs on 'starting'.

What am I doing wrong?

In addition to the code here, I have tried extensively wrapping different parts in try / catch blocks, but nothing is ever returned.

index.js:

const mysql = require('mysql');
const async = require('async');
const dbConfig = require('./db');
const employees = require('./employees');


async.series(
    [
        function(callback) {
            mysql.createConnection(dbConfig, function(err) {
                callback(err);

            });
        },
        function(callback) {
            employees.getEmployee(101, function(err, emp) {
                if (err) {
                    callback(err);
                    return;
                }

                console.log(emp);
            });
        }
    ],
    function(err) {
        if (err) {
            console.log(err);
        }
    }
);

employees.js:

const mysql = require('mysql');
const async = require('async');

function getEmployee(empId, getEmployeeCallback) {
    async.waterfall(
        [
            function(callback) {
                mysql.createConnection(function(err, conn) {
                    if (err) {
                        console.log('Error getting connection', err);
                    } else {
                        console.log('Connected to database');
                    }

                    callback(err, conn);
                });
            },
            function(conn, callback) {
                conn.execute(
                    `select *
          from employees`,

                    function(err, result) {
                        if (err) {
                            console.log('Error executing query', err);
                        } else {
                            console.log('Query executed');
                        }

                        callback(err, conn, result);
                    }
                );
            }
        ],
        function(err, conn, result) {
            if (err) {
                getEmployeeCallback(err);
            } else {
                getEmployeeCallback(null, result.rows[0]);
            }

            // If error getting conn, no need to close.
            if (conn) {
                conn.close(function(err) {
                    if (err) {
                        console.log('Error closing connection', err);
                    } else {
                        console.log('Connection closed');
                    }
                });
            }
        }
    );
}

module.exports.getEmployee = getEmployee;

db.js:

var mysql = require('mysql');

var connection = mysql.createConnection({
    host:'localhost',
    user:'developer',
    password:'superseceretpassword',
    database:'testing'
});


connection.connect(function(err) {
    if (err) throw err;
});

module.exports = connection;