Summing digits of factorials in Go

test.go

package main

import (
        "fmt"
        "math/big"
        "strings"
        "strconv"
        "time"
)

func Factorial(n *big.Int) *big.Int {
        var unit = big.NewInt(1)
        var acc *big.Int = big.NewInt(1)
        var t = n
        for t.Cmp(unit) == 1 {
                acc.Mul(acc, t)
                t.Sub(t, unit)
        }
        return acc
}

func SumDigits(n string) int64 {
        var r int64
        l := strings.Split(n, "")
        for i := 0; i < len(l); i++ {
                d, _ := strconv.ParseInt(l[i], 10, 0)
                r += d
        }
        return r
}

func main() {
        var s int64 = 0
        
        t1 := time.Now()
        n := []int64{1, 12, 123, 1234, 12345, 123456}
        for i := 0; i < len(n); i++ {
                r := Factorial(big.NewInt(n[i]))
                s += SumDigits(r.String())
        }
        t2 := time.Now()
        fmt.Printf("Elapsed time: %v\n", t2.Sub(t1))
        fmt.Println(s)
}