package main import "fmt" func filterEvenValuesInPlace(a []int) []int { // create a zero-length slice with the same underlying array res := a[:0] for _, v := range a { if v%2 == 0 { // collect only wanted values res = append(res, v) } } return res } func main() { a := []int{1, 2, 3, 4} res := filterEvenValuesInPlace(a) fmt.Printf("%#v\n", res) }