MyController.cs

[ApiController]
[Produces("application/json")]
[Route("api/[controller]/[action]")]
public class MyController : Controller {

  ...
  private readonly MyBackgroundService _myBackgroundService;
  
  public MyController(HostedService hostedService)
  {
      ...
      _myBackgroundService = hostedService as MyBackgroundService;
      ...
  }
  
  [HttpPost]
  public async Task<IActionResult> StartTask()
  {
      ...
      await _myBackgroundService.StartAsync(new System.Threading.CancellationToken());
      ...
  }

  [HttpPost]
  public async Task<IActionResult> StopTask()
  {
      ...
      await _myBackgroundService.StopAsync(new System.Threading.CancellationToken());
      ...
  }
}

~be