flashMessages is not working in newly create ember app

1. Create a new app using ember new testApp
2. Installed latest version of ember-cli-flash
3. created a test component
`import Component from "@glimmer/component";
import { inject as service } from "@ember/service";

export default class TestComponent extends Component {
@service flashMessages;

constructor() {
super(...arguments);
setTimeout(() => {
this.flashMessages.alert("dsfsf");
}, 1000)
}

}`
Calling TestComponent from application.hbs but flash message is not showing.