cache test and Update added

cache.go

@@ -109,6 +109,22 @@ func (c *cache) Replace(k string, x interface{}, d time.Duration) error {
 	return nil
 }
 
+// Update only if it is already existing, keep same ttl
+// Set new expiry time which is now - its expiration
+func (c *cache) Update(k string, x interface{}) error {
+	c.mu.Lock()
+	_, found := c.get(k)
+	if !found {
+		c.mu.Unlock()
+		return fmt.Errorf("Item %s doesn't exist", k)
+	}
+	newTtl := time.Unix(0, c.items[k].Expiration)
+	c.set(k, x, newTtl.Sub(time.Now()))
+	c.mu.Unlock()
+	return nil
+}
+
+
 // Get an item from the cache. Returns the item or nil, and a bool indicating
 // whether the key was found.
 func (c *cache) Get(k string) (interface{}, bool) {

sharded_test.go

@@ -27,7 +27,7 @@ var shardedKeys = []string{
 }
 
 func TestShardedCache(t *testing.T) {
-	tc := unexportedNewSharded(DefaultExpiration, 0, 13)
+	tc := NewSharded(DefaultExpiration, 0, 13)
 	for _, v := range shardedKeys {
 		tc.Set(v, "value", DefaultExpiration)
 	}
@@ -43,7 +43,7 @@ func BenchmarkShardedCacheGetNotExpiring(b *testing.B) {
 
 func benchmarkShardedCacheGet(b *testing.B, exp time.Duration) {
 	b.StopTimer()
-	tc := unexportedNewSharded(exp, 0, 10)
+	tc := NewSharded(exp, 0, 10)
 	tc.Set("foobarba", "zquux", DefaultExpiration)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
@@ -62,7 +62,7 @@ func BenchmarkShardedCacheGetManyConcurrentNotExpiring(b *testing.B) {
 func benchmarkShardedCacheGetManyConcurrent(b *testing.B, exp time.Duration) {
 	b.StopTimer()
 	n := 10000
-	tsc := unexportedNewSharded(exp, 0, 20)
+	tsc := NewSharded(exp, 0, 20)
 	keys := make([]string, n)
 	for i := 0; i < n; i++ {
 		k := "foo" + strconv.Itoa(n)