mat radio button checked not working

1/*  Use a FormControl instead 
2 *
3 *  <mat-radio-group [formControl]="radioFormControl">
4 *      <mat-radio-button [value]="1">Option 1</mat-radio-button>
5 *      <mat-radio-button [value]="2">Option 2</mat-radio-button>
6 *  </mat-radio-group>
7 */
8@Component({})
9export class RadioOverviewExample implements OnInit {
10    readonly radioFormControl = new FormControl(null);
11
12    ngOnInit() {
13        this.radioFormControl.setValue(1);
14    }
15}