Dividing work in a go (golang) port scanner

TodaysVersion.go

func ScanRangeTwo(min, max, num_threads int) (open_ports []string) {
	open_ch := make(chan []string, num_threads)
	high := min - 1
	for i := 0; i < num_threads; i++ {
		low := high + 1
		high = min + (i+1)*(max-min)/num_threads
		//fmt.Printf("Child #%d should scan %d through %d\n", i+1, low, high)
		go CheckRange(open_ch, low, high)
	}
	for i := 0; i < num_threads; i++ {
		result := <-open_ch
		open_ports = append(open_ports, result...)
	}
	return open_ports
}

YesterdaysVersion.go

func ScanRange(lower, upper int64) (open_ports []string) {
	open_ch := make(chan []string, threads)
	num_ports := int(upper - lower + 1)
	ports_per_thread := int(math.Ceil(float64(num_ports) / float64(threads)))
	fmt.Println("Ports per thread:", ports_per_thread)
	for i := 0; i < threads; i++ {
		child_lower := i*ports_per_thread + int(lower)
		child_upper := i*ports_per_thread + ports_per_thread
		if child_upper > num_ports {
			child_upper = num_ports
		}
		if child_lower > num_ports {
			child_lower = num_ports
		}
		//fmt.Printf("Child number %d about to try lower: %d - upper: %d\n", i, child_lower, child_upper)
		go CheckRange(open_ch, child_lower, child_upper)
	}
	waiting := threads
	for waiting > 0 {
		//fmt.Println("Waiting...", waiting)
		result := <-open_ch
		open_ports = append(open_ports, result...)
		waiting--
	}
	//fmt.Println("All children finished.")
	return open_ports
}