从异步函数分配

Question

我有一个server.js文件，我有：

const express = require('express');
const app = express();

let driver;

(async () => {    
  try {
    driver = await someAsyncFunction();
  } catch (err) {
    console.log(err);
  }
})();

const port = process.env.PORT;

app.listen(port, () => {
  console.log(`Server started on port ${port}.`);
});

module.exports = {
  app,
  driver,
};

但是，driver的值在异步函数之外是未定义的。如何在异步函数之外正确地为driver分配值？