Insert an element at a specific position using append:
s := []int{1, 2, 4, 5}
i := 2 // insert at index 2
s = append(s[:i], append([]int{3}, s[i:]...)...)
// s is now [1, 2, 3, 4, 5]
This pattern creates a temporary slice for the new element, appends the tail, then appends to the head. It's verbose but works for occasional insertions.