server := gateway.MustNewServer(config, gateway.WithMiddleware(authMiddleware))

server := gateway.MustNewServer(config, 
    gateway.WithMiddleware(authMiddleware, loggingMiddleware, rateLimitMiddleware))

server := gateway.MustNewServer(config, 
    gateway.WithMiddleware(authMiddleware),
    gateway.WithMiddleware(loggingMiddleware),
    gateway.WithMiddleware(rateLimitMiddleware))

func AuthMiddleware(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        // Pre-processing: check authentication
        token := r.Header.Get("Authorization")
        if !isValidToken(token) {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        
        // Call next middleware/handler
        next(w, r)
        
        // Post-processing: cleanup if needed
        // ...
    }
}