Go (golang) get all factors of an int

factors.go

// returns unsorted slice of *all* factors, not just primes
func getFactors(n int) []int {
    res := []int{}
    for i := 1; i <= int(math.Sqrt(float64(n))); i++ {
        if n%i == 0 {
            res = append(res, i)
            if i*i != n {
                res = append(res, n/i)
            }
        }
    }
    return res
}