How to correctly implement the launch of Koa with the preliminary initialization of the application?

Question

JavaScript

Before launching the Koa application (which should not be so important), I want to initialize the environment in which the application will work. For example, create a default user, set up a database, check the necessary directories, and so on. For example like this:

(async () => {
  await Promise.all([createDefaultUser()]); // тут всякое инициализирующее
})()
  .then(() => {
    logger.info(`Start serve on ${config.appHost}:${config.appPort}`);
    const server = app.listen(config.appPort, config.appHost);
  })
  .catch(err => {
    logger.error(`App initialization error: ${err}`);
  });

However, I still need to export server :

module.exports = server; // надо для нужд тестирования

And here's the stupor - either I can initialize the application before the server starts, but then I can't export, or I can export the server, but then the bolt is on initialization before the launch.
How is this done correctly?
Thank you.