<select class="form-control select2" id="cargoID" name="cargoID" style="width: 100%;" required>
    {% for cargo in cargos %}
        <option value="{{ cargo.cargoID }}">{{ cargo.cargoTITULO|striptags }}</option>
    {% endfor%}
</select>

<script type="text/javascript">
    $(document).ready(function() {
        $('.select2').select2();
    });
</script>