In Bootstrap 4, select option field doesn't support required="true" for simple validation

Question

I can't fixed this anymore. please help!

I already tried: required="required" also

<span class="channel">
           <select class="selectpicker" name="channel_id" data-style="btn btn-link" id="exampleFormControlSelect1" required="true">
                 <option>Channel</option>

               @foreach($channels as $channel)
                  <option value="{{ $channel->id }}">{{ $channel->title }}   
                 </option>
               @endforeach

            </select>
  </span>

If there is any other option in Bootstrap 4 please let me know.