go split number into intervals

Split number into intervals, so that each go routine can concurrent process part of the job.

func ToIntervals(start int64, end int64, interval int64) (intervals [][2]int64, err error) {
    if start > end {
        return nil, errors.New(fmt.Sprintf("invalid input %d %d %d, start > end", start, end, interval))
    }
    if interval < 0 {
        return nil, errors.New(fmt.Sprintf("invalid input %d %d %d, interval <= 0", start, end, interval))
    }
    if interval == 0 || interval > end-start {
        return [][2]int64{{start, end}}, nil
    }
    for i := start; i <= end; i += interval {
        if i+interval-1 > end {
            intervals = append(intervals, [2]int64{i, end})
            break
        }
        intervals = append(intervals, [2]int64{i, i + interval - 1})
    }
    return intervals, nil
}

test

func TestToIntervals(t *testing.T) {
    intervals, err := ToIntervals(0, 10, 3)
    t.Log(intervals, err) // [[0 2] [3 5] [6 8] [9 10]]
}