Delay an async method after the NestJS controller method response finish

Question

I have a @Get() method in a Controller. I get the response, but after the response is successfully I would like to call an async method after a delay of some milliseconds.

I'm using a Middleware, but seems like the response is pending for the time specified in the async method.

How can I do to solve the response in time, and after the delay call the custom method from the Custom Service?

Here is the used sample code:

@Controller()
export class CustomController {
  @Get("custom-controller-route")
  getCustomValue(@Res() response: Response) {
    return response.status(200).send({
       value: 1
    })
  }
}

The middleware code is the following:

@Injectable()
export class CustomMiddleware implements NestMiddleware {
  constructor(private readonly customService: CustomService) {}
  use(req: any, res: any, next: () => void) {
    let send = res.send
    res.send = async (customResponse: CustomResponse) => {
      const { value } = customResponse
      await customService.customMethod(value, 5000) // Delay of 5 seconds
      res.send = send
      return res.send(exchangeRateResponse)
    }
    next()
  }
}

And the CustomService has the next code:

@Injectable()
export class CustomService {
    async customMethod(value: any, delay) {
      await firstValueFrom(
        timer(delay).pipe(
          tap(() => {
            // Here is the logic that needs to be run in the delay time after the response is finished
           console.log(`Custom Service - custom method called with: ${value} after: ${delay} milliseconds.`)
          })
        )
      )
    }
}

Answer 1

I could do it instead of returning the response in the Controller method, I only call the res.status(200).send({}) with the specific response and after that I call the specific method call with the delay.

@Controller()
export class CustomController {
  @Get("custom-controller-route")
  getCustomValue(@Res() response: Response) {
   response.status(200).send({ value: 1 })
   // Call the delayed Service method
  }
}

Any other better option is welcome