How to determine which column I’m rendering in a 3 column bootstrap grid

I’m looping through a for loop to construct a row with 3 columns, where each column has a button.
I’d like to know if I’m in col 1, 2 or 3. I know I can get the odd and even cols from doing a % (mod) from the index, but not sure how to determine which of the 1st, 2nd or 3rd column it’s looking at.

Here is my code

<div class="row">
  <ng-container *ngFor="let program of instructedPrograms.value; let i = index">
    <div class="col-4">
      <button type="button" class="btn btn-outline-secondary w-100">
        {{i}} {{program}} {{(i % 2)}}
      </button>
    </div>
  </ng-container>
</div>

Source: Angular Questions