一个全排列的问题，用递归回溯给切片赋值，最后输出的是最后一次递归的数组。怎么解决这个问题，困扰了一上午。

package main

import (
    "fmt"
)

func swap(nums []int, i, j int) {
    temp := nums[i]
    nums[i] = nums[j]
    nums[j] = temp
}
func permute(nums []int) [][]int {
    length := len(nums) - 1
    var res [][]int
    dfs1(nums, 0, length, &res)
    fmt.Println(res)
    return res
}
func dfs1(nums []int, cur, end int, res *[][]int) {
    if cur == end {
        *res = append(*res, nums)
        return
    } else {
        for i := cur; i <= end; i++ {
            swap(nums, cur, i)
            dfs1(nums, cur+1, end, res)
            swap(nums, cur, i)
        }
    }
}

func main() {
    nums := []int{4, 5, 6}
    permute(nums)
}

输出的
[[4 5 6] [4 5 6] [4 5 6] [4 5 6] [4 5 6] [4 5 6]]