Go语言递归构建树状结构时，子节点为空的原因是什么及如何解决？

func getSysRegionTree(pid string, deep int) (error, []data.RegionTree) {
    var regionTree []data.RegionTree
    // 查询数据库
    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) // 假设ID是string类型
        fmt.Println("children count =", len(children))
        region.Children = children // 问题在此行，修改的是副本
    }

    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) // 同样修改的是副本
        }
    }
    return regionTree
}

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