Suggested fixes for last example in https://www.telerik.com/blogs/building-faster-backends-in-aspnet-core

building-faster-backends-in-aspnet-core-fix.cs

private async Task<List<Customer>> GetCustomerDataParallel()
{
  // Kick off all of these in parallel
  var customerTask = service.GetCustomersAsync();
  var detailsTask = service.GetExtraCustomerDataFromService();
  var moreDetailsTask = service.GetmoreExternalCustomerDataFromService();
  
  // Wait for everything to complete.
  await Task.WhenAll(customerTask, detailsTask, moreDetailsTask)
    .ConfigureAwait(false);
    
  return AssembleCustomerDetails(customerTask.Result, 
    detailsTask.Result, 
    moreDetailsTask.Result);
}