Merge Sort

package main
import ("fmt")
func MergeSort(arr []int) {
    size := len(arr)
    tempArray := make([]int, size)
    mergeSrt(arr, tempArray, 0, size-1)
}
func mergeSrt(arr []int, tempArray []int, lowerIndex int, upperIndex int) { 
  if lowerIndex >= upperIndex {
      return 
    }
    middleIndex := (lowerIndex + upperIndex) / 2 
    mergeSrt(arr, tempArray, lowerIndex, middleIndex) 
    mergeSrt(arr, tempArray, middleIndex+1, upperIndex)
    merge(arr, tempArray, lowerIndex, middleIndex, upperIndex)
}
func merge(arr []int, tempArray []int, lowerIndex int, middleIndex int, upperIndex int) {
    lowerStart := lowerIndex
    lowerStop := middleIndex
    upperStart := middleIndex + 1
    upperStop := upperIndex
    count := lowerIndex
    for lowerStart <= lowerStop && upperStart <= upperStop {
        if arr[lowerStart] < arr[upperStart] {
            tempArray[count] = arr[lowerStart]
            lowerStart++
        } else {
            tempArray[count] = arr[upperStart]
            upperStart++
    }
    count++
   }
    for lowerStart <= lowerStop {
        tempArray[count] = arr[lowerStart]
        count++
        lowerStart++
    }
    for upperStart <= upperStop {
        tempArray[count] = arr[upperStart]
        count++
        upperStart++
    }
    for i := lowerIndex; i <= upperIndex; i++ {
        arr[i] = tempArray[i]
    }
}
//Testing Code
func main() {
  data := []int{9, 1, 8, 2, 7, 3, 6, 4, 5} 
  MergeSort(data)
  fmt.Println(data)
}