Handle zero and negative expirations

cache.go

@@ -77,6 +77,9 @@ type itemOptions struct {
 // WithExpiration is an option to set expiration time for any items.
 // If the expiration is zero or negative value, it treats as w/o expiration.
 func WithExpiration(exp time.Duration) ItemOption {
+	if exp <= 0 {
+		return func(o *itemOptions) {}
+	}
 	return func(o *itemOptions) {
 		o.expiration = nowFunc().Add(exp)
 	}

cache_internal_test.go

@@ -9,11 +9,17 @@ import (
 func TestDeletedCache(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
+	restore := func() {
+		nowFunc = time.Now
+	}
+	defer restore()
 
 	nc := NewContext[string, int](ctx)
 	key := "key"
-	nc.Set(key, 1, WithExpiration(-time.Second))
-
+	nc.Set(key, 1, WithExpiration(1*time.Second))
+	nowFunc = func() time.Time {
+		return time.Now().Add(2 * time.Second)
+	}
 	_, ok := nc.cache.Get(key)
 	if !ok {
 		t.Fatal("want true")
@@ -143,6 +149,30 @@ func TestDeleteExpired(t *testing.T) {
 			t.Errorf("want %d items but got %d", want, got)
 		}
 	})
+
+	t.Run("issue #64", func(t *testing.T) {
+		defer restore()
+		c := New[string, int]()
+		c.Set("1", 4, WithExpiration(0))  // These should not be expired
+		c.Set("2", 5, WithExpiration(-1)) // These should not be expired
+		c.Set("3", 6, WithExpiration(1*time.Hour))
+
+		want := true
+		_, ok := c.Get("1")
+		if ok != want {
+			t.Errorf("want %t but got %t", want, ok)
+		}
+
+		_, ok = c.Get("2")
+		if ok != want {
+			t.Errorf("want %t but got %t", want, ok)
+		}
+		_, ok = c.Get("3")
+		if ok != want {
+			t.Errorf("want %t but got %t", want, ok)
+		}
+
+	})
 }
 
 func max(x, y int) int {