嵌套

https://go.dev/play/p/lcQg8rXk03I

t.go

package main

import (
    "encoding/json"
    "fmt"

    "github.com/samber/lo"
)

type Item struct {
    Id       int
    Name     string
    Pid      int
    Children []Item
}

func toNested(list []Item, pid int) []Item {
    return lo.Reduce(list, func(agg []Item, item Item, index int) []Item {
        if pid == item.Pid {
            item.Children = toNested(list, item.Id)
            return append(agg, item)
        } else {
            return agg
        }

    }, []Item{})
}

func main() {

    list := []Item{
        Item{
            Id:   1,
            Name: "1",
            Pid:  0,
        },
        Item{
            Id:   2,
            Name: "1-2",
            Pid:  1,
        },
        Item{
            Id:   3,
            Name: "3",
            Pid:  0,
        },
        Item{
            Id:   4,
            Name: "4",
            Pid:  0,
        },
        Item{
            Id:   5,
            Name: "4-5",
            Pid:  4,
        },
        Item{
            Id:   6,
            Name: "1-2-6",
            Pid:  2,
        },
    }

    result := toNested(list, 0)
    fmt.Printf("%v\n", result)

    jsonb, _ := json.Marshal(result)
    fmt.Println(string(jsonb))
}