go question

blah.go

package main

func modify (myarr *[]int) {
  myarr = append(*myarr, 4)
}

func main() {
  arr := []int{}
  arr = append(arr, 1)
  arr = append(arr, 2)
  arr = append(arr, 3)
  println(len(arr))
  modify(&arr)
  println(len(arr))
  s := 0
  for _, v := range arr {
    s = s + v
  }
  println("Result:", s)
}