[Go] Higher-order function: reduce

package main

import (
    "log"
)

func reduce(arr []int, reducer func(int, int) int) int {
    if len(arr) == 0 {
        return 0
    } else if len(arr) == 1 {
        return arr[0]
    }

    n := arr[0]

    for i := 1; i < len(arr); i++ {
        n = reducer(n, arr[i])
    }

    return n
}

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

    n := reduce(arr, func(a int, b int) int { return a + b })

    if !(n == 15) {
        log.Fatal("Wrong value")
    }
}