add GetWithExpirationUpdate

cache.go

@@ -165,6 +165,38 @@ func (c *cache) GetWithExpiration(k string) (interface{}, time.Time, bool) {
 return item.Object, time.Time{}, true
 }
 
+// GetWithExpirationUpdate returns item and updates its cache expiration time
+// It returns the item or nil, the expiration time if one is set (if the item
+// never expires a zero value for time.Time is returned), and a bool indicating
+// whether the key was found.
+func (c *cache) GetWithExpirationUpdate(k string, d time.Duration) (interface{}, bool) {
+c.mu.RLock()
+item, found := c.items[k]
+if !found {
+c.mu.RUnlock()
+return nil, false
+}
+if item.Expiration > 0 {
+if time.Now().UnixNano() > item.Expiration {
+c.mu.RUnlock()
+return nil, false
+}
+}
+c.mu.RUnlock()
+
+c.mu.Lock()
+if d == DefaultExpiration {
+d = c.defaultExpiration
+}
+if d > 0 {
+item.Expiration = time.Now().Add(d).UnixNano()
+}
+c.items[k] = item
+c.mu.Unlock()
+
+return item.Object, true
+}
+
 func (c *cache) get(k string) (interface{}, bool) {
 item, found := c.items[k]
 if !found {

cache_test.go

@@ -1769,3 +1769,28 @@ func TestGetWithExpiration(t *testing.T) {
 t.Error("expiration for e is in the past")
 }
 }
+
+func TestGetWithExpirationUpdate(t *testing.T) {
+var found bool
+
+tc := New(50*time.Millisecond, 1*time.Millisecond)
+tc.Set("a", 1, DefaultExpiration)
+
+<-time.After(25 * time.Millisecond)
+_, found = tc.GetWithExpirationUpdate("a", DefaultExpiration)
+if !found {
+	t.Error("item `a` not expired yet")
+}
+
+<-time.After(25 * time.Millisecond)
+_, found = tc.Get("a")
+if !found {
+t.Error("item `a` not expired yet")
+}
+
+<-time.After(30 * time.Millisecond)
+_, found = tc.Get("a")
+if found {
+t.Error("Found `a` when it should have been automatically deleted")
+}
+}