Go语言递归构建树状结构时，子节点为空的原因及解决方法是什么？

func getSysRegionTree(pid string, deep int) (err error, result []data.RegionTree) {
    var regionTree []data.RegionTree
    // 数据库查询
    err = tx.Model(&model.SysRegion{}).Where("pid = ? and enabled = true", pid).Order("id asc").Find(&regionTree).Error
    if err != nil {
        panic(err)
    }

    for _, region := range regionTree {
        children := findChildren(tx, region.id, deep-1)
        fmt.Println("children count =", len(children)) // children count 始终为0
        region.Children = children // children 赋值后仍然为空
    }

    return err, regionTree
}

func findChildren(tx *gorm.DB, pid string, left int) []data.RegionTree {
    var regionTree []data.RegionTree
    err := tx.Model(&model.SysRegion{}).Where("pid = ? and enabled = true", pid).Order("id desc").Find(&regionTree).Error
    if err != nil {
        panic(err)
    }
    if left > 1 {
        for _, region := range regionTree {
            region.Children = findChildren(tx, region.id, left-1) // 这里的问题在于region是副本
        }
    }
    return regionTree
}

for i, region := range regionTree {
    children := findChildren(tx, region.id, deep-1)
    regionTree[i].Children = children
}