have fixed card-action at bottom fixed bootstrap 4 code example
Example: boostrap card
<div class="card" style="width: 18rem;">
<div class="card-body">
<h5 class="card-title">Card title</h5>
<h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
<p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
<a href="#" class="card-link">Card link</a>
<a href="#" class="card-link">Another link</a>
</div>
</div>