How is user access control implemented in the system?

User access control to the system is the process of verifying and managing user rights to perform certain actions or access resources.

Main stages of access control:

1. Authentication — verifying the user's identity (e.g., entering login and password).
2. Authorization — determining what actions are permitted for the authenticated user.
3. Audit — recording and analyzing user actions for security.

In Go, this is often implemented through middleware that checks tokens or sessions and then determines access rights.

Example of simple middleware for authorization check:

func AuthMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token := r.Header.Get("Authorization")
        if !isValidToken(token) {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        next.ServeHTTP(w, r)
    })
}

func isValidToken(token string) bool {
    // Token validation logic
    return token == "valid-token"
}

Thus, access control ensures security and proper rights distribution within the system.