Custom Product page meta resolver not getting called

I am trying to add Meta Description to my PDP page in Spartacus 6.5.I'm adding my resolver extended from ProductPageMetaResolver into providers in my custom product.module.However, my method 'resolveDescription' is not called. Am I missing anything?

Here is my code :

@Injectable({   providedIn: 'root'}) export class MyProductPageMetaResolverService extends ProductPageMetaResolver {resolveDescription(): Observable<string> {alert("test")return this.product$.pipe(  switchMap((product) =>    this.translation.translate('pageMetaResolver.product.description', {      description: "Test Description"    })))}}

and in product.module:

providers: [{ provide: PageMetaResolver, useExisting: MyProductPageMetaResolverService, multi: true},.........