Counting sort

package main

import (
	"fmt"
	"math/rand"
	"time"
)

func CountingSort(list []int, min int, max int) ([]int, error) {

	if max < min {
		return nil, fmt.Errorf("range is not valid")
	}

	if max == min {
		return list, nil
	}

	offset := min
	length := (max - min + 1)
	counts := make([]int, length)
	for _, elm := range list {
		counts[elm-offset]++
	}

	for i := 1; i < length; i++ {
		counts[i] = counts[i] + counts[i-1]
	}

	var res []int = make([]int, len(list))
	for j := len(list) - 1; j >= 0; j-- {
		res[counts[list[j]-offset]-1] = list[j]
		counts[list[j]-offset]--
	}

	return res, nil
}

func init() {
	rand.Seed(time.Now().Unix())
}

func main() {

	min, max := -3, 15
	length := 10
	var list []int
	for j := 0; j < length; j++ {
		list = append(list, rand.Intn(max-min+1)+min)
	}
	fmt.Println(list)

	// O(n)
	result, err := CountingSort(list, min, max)
	if err != nil {
		panic(err)
	}
	fmt.Println(result)
}