getFolders(folderId: string): Observable<{ id: string, name: string }[]> {
    const promise = gapi.client.drive.files.list({
      fields: 'incompleteSearch,nextPageToken,files(id,name)',
      q: `'${folderId}' in parents`,
    }).then((res) => {
      return JSON.parse(res.result.files);
    });
    return from(promise);
  }

this.data$ = this.googleDriveService.getFolders(rootFolderId)
        .pipe(
          map((files) => {
            debugger;
            return files.map(file => ({ id: file.id, header: file.name, content: '', imageUrl: this.defaultImageUrl }));
          }),
          takeUntil(this.destroy$),
        );

<mat-grid-tile *ngFor="let elem of (data$ | async)">
    <app-card (input)="returnCartItem(elem)" (click)="goto(elem.header, elem.id)"></app-card>
  </mat-grid-tile>