How to save authUser object from middleware into request [fastify]

I wanted to save authUser object into fastify request before it comes into handler.

I did it like this in router.

        method: 'GET',
        url: '/user',
        preHandler: (
        handler: controllers.getAllUsers

But It always comes into handler before it’s getting it from db. so, that means I can’t run async function into middleware in fastify?