func productExceptSelf(nums []int) []int {
    res:=make([]int,len(nums))

    prefix:=1
    for i:= range nums {
        res[i] = prefix
        prefix *=nums[i]
    }
    postfix:=1
    for i:=len(nums) -1;i>=0;i-- {
        res[i] *=postfix
        postfix *=nums[i]
    }
    return res
}