// RecursiveList 递归处理list
func RecursiveList(list []model.XfArticleCategory, pid int) []model.XfArticleCategory {
    res := make([]model.XfArticleCategory, 0)
    for _, v := range list {
        if v.Category_pid == pid {
            v.Child = RecursiveList(list, v.Id)
            if v.Child == nil {
                v.Child = make([]model.XfArticleCategory, 0)
            }
            res = append(res, v)
        }
    }
    return res
}