func NewMongoStore(config MongoConfig) (*MongoStore, error) {
	var session *mgo.Session
	if config.URL != "" {
		s, err := mgo.Dial(config.URL)
		if err != nil {
			return nil, err
		}
		session = s
	} else if config.Session != nil {
		session = config.Session
	} else {
		return nil, errors.New("未知的MongoDB连接")
	}
	if config.Collection == "" {
		config.Collection = DefaultCollection
	}
	return &MongoStore{
		config:  config,
		session: session,
		lg:      log.New(os.Stdout, "[Mongo-Store]", log.LstdFlags),
	}, nil
}
func NewMongoStore(config MongoConfig) (*MongoStore, error) {
	var session *mgo.Session
	if config.URL != "" {
		s, err := mgo.Dial(config.URL)
		if err != nil {
			return nil, err
		}
		session = s
	} else if config.Session != nil {
		session = config.Session
	} else {
		return nil, errors.New("未知的MongoDB连接")
	}
	if config.Collection == "" {
		config.Collection = DefaultCollection
	}
	return &MongoStore{
		config:  config,
		session: session,
		lg:      log.New(os.Stdout, "[Mongo-Store]", log.LstdFlags),
	}, nil
}
// NewMongoStore 创建敏感词MongoDB存储