Go Max Slice Sum
func maxSliceSum(a []int) int {
	tmp, best := math.MinInt, math.MinInt

	for _, v := range a {
		if tmp+v > v {
			tmp += v
		} else {
			tmp = v
		}
		if tmp > best {
			best = tmp
		}
	}

	return best
}

This is a Kadane-style scan: keep the best running sum and the best overall sum while moving once through the array.