How to use the base in modules?

Question

Node.js

I have a module in which the database is connected, I need to use it in all Express routers.
I could create a new connection, but I would like to somehow pass the class of work with the base through the context.
Please help me with advice to solve this problem.

app.use("/method", require("./test"));

const { Router } = require("express");
const router = Router();

router.get("/register", async (req, res) => {
  const user = await db.query("SELECT * FROM `users`");
  res.status(200).json({ result: { user } });
});

module.exports = router;

Here somehow it is necessary to transfer the class