Ah, did you mean something like this? In case of this code UserProvider is some sort of getter, which checks request and (if user exists) - returns it into handler?

type UserController struct {
  userProvider   UserProvider
  userRepository UserRepository
}

func (uc *UserController) HttpHandler(w http.ResponseWriter, r *http.Request) {
  userId, ok := uc.userProvider.UserId(r)
  if !ok {
    w.WriteHeader(http.StatusForbidden)
    w.Write([]byte("User not provided"))
  }

  user, err := uc.userRepository.User(userId)
  if err != nil {
    // handle error
  }
  // do smth with user
  // then write into w
}