Remove the item's mutex. doPromote can only happen in a single goroutine.

Bucket.set has its own lock which would prevent an item from being accessed
by multiple goroutines.

bucket.go

@@ -17,14 +17,12 @@ func (b *Bucket) get(key string) *Item {
 }
 
 func (b *Bucket) set(key string, value interface{}, duration time.Duration) (*Item, bool) {
-	expires := time.Now().Add(duration)
+	expires := time.Now().Add(duration).Unix()
 	b.Lock()
 	defer b.Unlock()
 	if existing, exists := b.lookup[key]; exists {
-		existing.Lock()
 		existing.value = value
-		existing.expires = expires.Unix()
-		existing.Unlock()
+		existing.expires = expires
 		return existing, false
 	}
 	item := newItem(key, value, expires)

cache.go

@@ -137,8 +137,6 @@ func (c *Cache) worker() {
 }
 
 func (c *Cache) doPromote(item *Item) bool {
-	item.Lock()
-	defer item.Unlock()
 	item.promotions = 0
 	if item.element != nil { //not a new item
 		c.list.MoveToFront(item.element)

item.go

@@ -2,9 +2,7 @@ package ccache
 
 import (
 	"container/list"
-	"sync"
 	"sync/atomic"
-	"time"
 )
 
 type TrackedItem interface {
@@ -21,7 +19,6 @@ var NilTracked = new(nilItem)
 
 type Item struct {
 	key string
-	sync.Mutex
 	promotions int32
 	refCount   int32
 	expires    int64
@@ -29,12 +26,12 @@ type Item struct {
 	element    *list.Element
 }
 
-func newItem(key string, value interface{}, expires time.Time) *Item {
+func newItem(key string, value interface{}, expires int64) *Item {
 	return &Item{
 		key:        key,
 		value:      value,
 		promotions: -1,
-		expires:    expires.Unix(),
+		expires:    expires,
 	}
 }