How to implement authorization in Express-gateway through a custom microservice?

Question

JSON Web Token

Good day to all. I'm new to implementing microservice architecture and I was advised to use ready-made solutions like Express-gateway instead of implementing my own API Gateway. After reading a little about this solution, I roughly understood the principle of operation, but the question remained open for me, how to authenticate users using a custom microservice? The architecture is such that I have my own microservice that implements the user registration and authorization logic, and then generates two tokens (one for authorization, the second for issuing access rights), these tokens are sent to all microservices through a broker. And according to the logic of Express-Gateway, the authorization token will be checked in the same place on the API Gateway.
Anyone who has experienced this, your advice would be very helpful)) Thank you in advance))