go新手求问，为什么结果不同？

package main

import (
    "fmt"
)

func main() {
    var arr []int
    setArr(&arr)
    fmt.Printf("point behand: %p,value behand: %v \n", arr, arr)
}
func setArr(arr *[]int) {
    arr1 := &[]int{1, 2}
    arr = arr1
    fmt.Printf("point before: %p,value before: %v \n", arr, arr)
} 
输出：
point before: 0xc42000a260,value before: &[1 2]
point behand: 0x0,value behand: []