HealthCheckController.cs

[Route("api/[controller]")]
public class HealthCheckController : Controller
{
    private readonly IHealthCheckService _healthCheckService;

    public HealthCheckController(IHealthCheckService healthCheckService)
    {
        _healthCheckService = healthCheckService;
    }

    [HttpGet]
    public async Task<IActionResult> Get()
    {
        // Can also call RunCheckAsync to run a single Heatlh Check or RunGroupAsync to run a group of Health Checks
        CompositeHealthCheckResult healthCheckResult = await _healthCheckService.CheckHealthAsync();

        bool somethingIsWrong = healthCheckResult.CheckStatus != CheckStatus.Healthy;

        if (somethingIsWrong)
        {
            // healthCheckResult has a .Description property, but that shows the description of all health checks. 
            // Including the successful ones, so let's filter those out
            var failedHealthCheckDescriptions = healthCheckResult.Results.Where(r => r.Value.CheckStatus != CheckStatus.Healthy)
                                                                 .Select(r => r.Value.Description)
                                                                 .ToList();

            // return a 500 with JSON containing the Results of the Health Check
            return new JsonResult(new {Errors = failedHealthCheckDescriptions}){ StatusCode = StatusCodes.Status500InternalServerError };
        }

        return Ok();
    }
}