The impact of append and slice operations on array contents

Determine what output the program will produce when it is run:

package main

import "fmt"

func foo(s []int) {
    s = append(s, 5)
}

func main() {
    base := []int{1, 2, 3}
    slice := base[:1]

    foo(slice)

    fmt.Println(slice)
    fmt.Println(base)
}