新增动态大小的安全队列gqueue，并修正grpool关闭时的数量问题

g/container/gqueue/string_queue.go

@@ -0,0 +1,54 @@
+// Copyright 2017 gf Author(https://gitee.com/johng/gf). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://gitee.com/johng/gf.
+
+package gqueue
+
+import (
+    "math"
+    "sync"
+    "container/list"
+)
+
+type StringQueue struct {
+    mu     sync.RWMutex
+    list   *list.List
+    events chan struct{}
+}
+
+func NewStringQueue() *StringQueue {
+    return &StringQueue{
+        list   : list.New(),
+        events : make(chan struct{}, math.MaxInt64),
+    }
+}
+
+// 将数据压入队列
+func (q *StringQueue) Push(v string) {
+    q.mu.Lock()
+    q.list.PushBack(v)
+    q.mu.Unlock()
+    q.events <- struct{}{}
+}
+
+// 先进先出地从队列取出一项数据，当没有数据可获取时，阻塞等待
+func (q *StringQueue) Pop() string {
+    select {
+        case <- q.events:
+            q.mu.Lock()
+            if elem := q.list.Front(); elem != nil {
+                item := q.list.Remove(elem).(string)
+                q.mu.Unlock()
+                return item
+            }
+            q.mu.Unlock()
+    }
+    return ""
+}
+
+// 获取当前队列大小
+func (q *StringQueue) Size() int {
+    return len(q.events)
+}