Subscribing to a topic with the NestJS Microservice with Redis

I have a controller setup like so:

@Controller()
export class AppController {
  constructor(private readonly appService: AppService) {}

  @EventPattern({ cmd: 'SUBSCRIBE a' })
  getHello(@Payload() data, @Ctx() context: RedisContext) {
    console.log(data);
    console.log(context);
    //return this.appService.getHello();
  }
}

My bootstrap code looks like this:

  const app = await NestFactory.createMicroservice<MicroserviceOptions>(
    AppModule,
    {
      transport: Transport.REDIS,
      options: {
        url: 'redis://localhost:6379',
      },
    },
  );
  app.listen(() => console.log('listening'));

How do I set I subscribe to a Redis topic? I checked the Redis CLI, and there are currently no subscribers. I want to consume messages from the controller based on a topic name.

I tried everything: @EventPattern({ cmd: 'SUBSCRIBE a' }), @EventPattern({ cmd: 'a' })...

None of the docs mention how to subscribe to a topic.