how to add button to ion-select alert in ionic 4 code example

Example 1: ionic select

<ion-list>
  <ion-list-header>
    <ion-label>
      Single Selection
    </ion-label>
  </ion-list-header>

  <ion-item>
    <ion-label>Gender</ion-label>
    <ion-select placeholder="Select One">
      <ion-select-option value="f">Female</ion-select-option>
      <ion-select-option value="m">Male</ion-select-option>
    </ion-select>
  </ion-item>

  <ion-item>
    <ion-label>Hair Color</ion-label>
    <ion-select value="brown" okText="Okay" cancelText="Dismiss">
      <ion-select-option value="brown">Brown</ion-select-option>
      <ion-select-option value="blonde">Blonde</ion-select-option>
      <ion-select-option value="black">Black</ion-select-option>
      <ion-select-option value="red">Red</ion-select-option>
    </ion-select>
  </ion-item>

</ion-list>

Example 2: ion-select cancel text

<ion-select cancel-text="Cancelar">
	<ion-select-option *ngFor="let country of countries" value="{{ country.name }}">
		{{ country.name }}
	</ion-select-option>
</ion-select>