type SafeMap struct {
    sync.RWMutex
    Map map[int64]string
}

func NewSafeMap(size int) *SafeMap {
    sm := new(SafeMap)
    sm.Map = make(map[int64]string,size)
    return sm
}

func (sm *SafeMap) ReadMap(key int64) string {
    sm.RLock()
    value := sm.Map[key]
    sm.RUnlock()
    return value
}

func (sm *SafeMap) WriteMap(key int64,value string) {
    sm.Lock()
    sm.Map[key] = value
    sm.Unlock()
}

// 用于for k，_ := range m.Keys(){v := m.ReadMap(k) ....}
func (sm *SafeMap) Keys() []int64 {
    sm.RLock()
    value := make([]int64, 0)
    for k,_ := range sm.Map {
        value = append(value,k)
    }
    sm.RUnlock()
    return value
}