Fix: use correctly last record

adapters/outbound/base.go

@@ -114,11 +114,11 @@ func (p *Proxy) LastDelay() (delay uint16) {
 		return max
 	}
 
-	head := p.history.First()
-	if head == nil {
+	last := p.history.Last()
+	if last == nil {
 		return max
 	}
-	history := head.(C.DelayHistory)
+	history := last.(C.DelayHistory)
 	if history.Delay == 0 {
 		return max
 	}

common/queue/queue.go

@@ -34,16 +34,16 @@ func (q *Queue) Pop() interface{} {
 	return head
 }
 
-// First returns the head of items without deleting.
-func (q *Queue) First() interface{} {
+// Last returns the last of item.
+func (q *Queue) Last() interface{} {
 	if len(q.items) == 0 {
 		return nil
 	}
 
 	q.lock.RLock()
-	head := q.items[0]
+	last := q.items[len(q.items)-1]
 	q.lock.RUnlock()
-	return head
+	return last
 }
 
 // Copy get the copy of queue.