Leetcode 56

func merge(intervals [][]int) [][]int {
    res := [][]int{}
    for i := 1; i < len(intervals); i++ {
        if i >= 1 && intervals[i-1][0] > intervals[i][0] {
            
            intervals[i-1], intervals[i] = 
            intervals[i], intervals[i-1]
            
            i -= 2
        }
    }
    res = append(res, intervals[0])
    for i := 1; i < len(intervals); i++ {
        if res[len(res)-1][1] >= intervals[i][0] {
        
            res[len(res)-1][1] = 
            max(intervals[i][1], res[len(res)-1][1])
            
        } else {
            res = append(res, intervals[i])
        }
    }

    return res
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}