...
export * from './test/index';

...
export * from './my-service.service';

import { MyService } from '../../core';
...

@Injectable()
export class AuthGuard implements CanActivate {
    isValidSession: boolean = false;
    errorMessage: any;

    constructor(
        private myService: MyService
    ) { }

    canActivate(
        // Not using but worth knowing about
        next: ActivatedRouteSnapshot,
        state: RouterStateSnapshot
    ) {
        return this.myService.doSomething();
    }
}

import { MyService } from '../../core/test/my-service.service';

import { MyService } from '../../core/test';