[Go] Higher-order function: apply

package main

import (
    "log"
)

// map is predefined word in Go. Use apply instead.
func apply(arr []int, mapper func(int) int) []int {
    out := make([]int, len(arr))

    for i, e := range arr {
        out[i] = mapper(e)
    }

    return out
}

// eq declared as before.

func main() {
    arr := []int{1, 2, 3, 4, 5}

    out := apply(arr, func(n int) int { return n * n })

    if !eq(out, []int{1, 4, 9, 16, 25}) {
        log.Fatal("Wrong value")
    }
}