time complexity is O(n) because we do at most, one iteration through the array where n is the length of the array. Space complexity is constant since we have an input array and 3 variables we are using (curr, max and i)

maximum_subarray.go

import "math"

func maxSubArray(nums []int) int {
    if nums == nil { return 0 }
    
    curr := nums[0]
    max := curr
    
    for i := 1; i < len(nums); i++ {
        curr = int(math.Max(float64(curr + nums[i]), float64(nums[i])))
        if curr > max {
            max = curr
        }
    }
    
    return max
}