diff --git a/main.go b/main.go
index 81464f6..6ec6462 100644
--- a/main.go
+++ b/main.go
@@ -8,9 +8,9 @@ import (
 
 // Errors for cache
 const (
-	ErrKeyNotFound = "Key not found"
-	ErrKeyExists   = "Key already exists"
-	ErrExpired     = "Key expired"
+	ErrKeyNotFound = "key not found"
+	ErrKeyExists   = "key already exists"
+	ErrExpired     = "key expired"
 )
 
 // CacheItem is a struct for cache item
@@ -36,10 +36,16 @@ type Cacher interface {
 }
 
 // NewCache is a constructor for Cache
-func NewCache() *Cache {
-	return &Cache{
+func NewCache(options ...func(*Cache)) *Cache {
+	c := &Cache{
 		data: make(map[string]CacheItem),
 	}
+
+	for _, option := range options {
+		option(c)
+	}
+
+	return c
 }
 
 // Set is a method for setting key-value pair
@@ -143,3 +149,15 @@ func (c *Cache) Cleanup() {
 	}
 	c.mx.Unlock()
 }
+
+// WithCleanup is a functional option for setting interval and starting Cleanup goroutine
+func WithCleanup(ttl int64) func(*Cache) {
+	return func(c *Cache) {
+		go func() {
+			for {
+				c.Cleanup()
+				time.Sleep(time.Duration(ttl) * time.Second)
+			}
+		}()
+	}
+}
diff --git a/main_test.go b/main_test.go
index 26ddf83..76bdc25 100644
--- a/main_test.go
+++ b/main_test.go
@@ -100,6 +100,7 @@ func Test_SimpleTest_Mcache(t *testing.T) {
 	// key should be deleted
 	has, err = c.Has("key")
 	assert.False(t, has)
+	assert.Error(t, err)
 
 	// del should return error if key doesn't exist
 	err = c.Del("noSuchKey")
@@ -145,6 +146,26 @@ func TestConcurrentSetAndGet(t *testing.T) {
 	}
 }
 
+// TestWithCleanup tests that the cleanup goroutine is working
+func TestWithCleanup(t *testing.T) {
+	cache := NewCache(WithCleanup(1))
+
+	// Set a value with a TTL of 1 second
+	err := cache.Set("key", "value", 1)
+	if err != nil {
+		t.Errorf("Error setting value for key: %s", err)
+	}
+
+	// Wait for 2 seconds
+	time.Sleep(2 * time.Second)
+
+	// Check that the value has been deleted
+	_, err = cache.Get("key")
+	if err == nil {
+		t.Errorf("Expected error getting value for key, but got nil")
+	}
+}
+
 func TestMain(m *testing.M) {
 	// Enable the race detector
 	m.Run()