Use middleware only for json server specific routes

Question

How can I use a middleware ONLY FOR my json-server specific routes? In the json-server docs, I can see the following instructions:

const jsonServerRouter = jsonServer.router('mock-server/db.json')


server.use(customMiddleware)
server.use(jsonServerRouter) // customMiddleware should be executed ONLY FOR this jsonServerRouter

/*
Problem is here, customMiddleware has already been executed,
so following routes will use the middleware too
*/
server.use(otherRoutes)

What I've tried:

// This syntax is similar to the previous code. So it doesnt work
server.use(customMiddleware, jsonServerRouter)

// Passing the middleware to the 'router' function doesnt work
const jsonServerRouter = jsonServer.router('mock-server/db.json', customMiddleware)