How to make express-oauth-server?

Question

OAuth

There is such a module https://github.com/oauthjs/express-oauth-server . How to make a working server with oAuth2 on it, something cannot be done + in the examples one thing, but in fact the result is different. For example, in the example https://github.com/oauthjs/express-oauth-server/bl... there is a getClient method. It says that clientID and clientSecret get there, but in fact clientSecret doesn't get there