How to fix button location at the bottom

Ionic Framework ionic-v3
1

I want button to be stay at the bottom not in center


<ion-content class="cards-bg social-cards">
  <ion-card>
    <ion-item>
      <textarea #myInput id="myInput" rows="1" maxLength="500" (keyup)="resize()" [(ngModel)]="myStuff" placeholder="post comment"></textarea>
      <button id="mybtn" ion-button outline item-end icon-left>
        <ion-icon name="send"></ion-icon>
      </button>
    </ion-item>
  </ion-card>
css
.mybtn  {
  margin-bottom: 0px;
  margin-top: auto;
  margin-left: auto;
  margin-left: 0px;
}