Solution2.go

func CheckPermutation(s1 string, s2 string) bool {
	cs1, cs2 := []byte(s1), []byte(s2)
	sort.Slice(cs1, func(i, j int) bool { return cs1[i] < cs1[j] })
	sort.Slice(cs2, func(i, j int) bool { return cs2[i] < cs2[j] })
	return string(cs1) == string(cs2)
}