fix(api): disable cache middleware for non-positive ttl

Co-Authored-By: Virgil <virgil@lethean.io>

cache_test.go

@@ -327,6 +327,31 @@ func TestWithCache_Good_PreservesCurrentRequestMetaOnHit(t *testing.T) {
 	}
 }
 
+func TestWithCache_Ugly_NonPositiveTTLDisablesMiddleware(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	grp := &cacheCounterGroup{}
+	e, _ := api.New(api.WithCache(0))
+	e.Register(grp)
+
+	h := e.Handler()
+
+	for i := 0; i < 2; i++ {
+		w := httptest.NewRecorder()
+		req, _ := http.NewRequest(http.MethodGet, "/cache/counter", nil)
+		h.ServeHTTP(w, req)
+		if w.Code != http.StatusOK {
+			t.Fatalf("expected request %d to succeed with disabled cache, got %d", i+1, w.Code)
+		}
+		if got := w.Header().Get("X-Cache"); got != "" {
+			t.Fatalf("expected no X-Cache header with disabled cache, got %q", got)
+		}
+	}
+
+	if grp.counter.Load() != 2 {
+		t.Fatalf("expected counter=2 with disabled cache, got %d", grp.counter.Load())
+	}
+}
+
 func TestWithCache_Good_ExpiredCacheMisses(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	grp := &cacheCounterGroup{}

options.go

@@ -307,12 +307,16 @@ func timeoutResponse(c *gin.Context) {
 //
 // An optional maxEntries limit enables LRU eviction when the cache reaches
 // capacity. A value <= 0 keeps the cache unbounded for backward compatibility.
+// A non-positive TTL disables the middleware entirely.
 //
 // Example:
 //
 //	engine, _ := api.New(api.WithCache(5*time.Minute, 100))
 func WithCache(ttl time.Duration, maxEntries ...int) Option {
 	return func(e *Engine) {
+		if ttl <= 0 {
+			return
+		}
 		limit := 0
 		if len(maxEntries) > 0 {
 			limit = maxEntries[0]