find the kth smallest number in a list in go

main.go
func findKthSmallest(arr []int, k int) int {
  n := len(arr)
  left, right := 0, n-1
  for left <= right {
    pivotIndex := partition(arr, left, right)
    if pivotIndex == k-1 {
      return arr[pivotIndex]
    } else if pivotIndex > k-1 {
      right = pivotIndex - 1
    } else {
      left = pivotIndex + 1
    }
  }
  return -1
}

func partition(arr []int, left, right int) int {
  pivotIndex := left
  for i := left; i < right; i++ {
    if arr[i] < arr[right] {
      arr[i], arr[pivotIndex] = arr[pivotIndex], arr[i]
      pivotIndex++
    }
  }
  arr[pivotIndex], arr[right] = arr[right], arr[pivotIndex]
  return pivotIndex
}
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