static async Task Cleanup(IDelegatingHandler handler)
 {
     try
     {
         if (handler != null)
         {
             await handler.CloseAsync().ConfigureAwait(false);
         }
     }
     catch (Exception ex) when(!ex.IsFatal())
     {
         //unexpected behaviour - ignore. LOG?
     }
 }
 async void Cleanup(IDelegatingHandler handler)
 {
     try
     {
         if (handler != null)
         {
             await handler.CloseAsync();
         }
     }
     catch (Exception ex) when(!ex.IsFatal())
     {
         //unexpected behaviour - ignore. LOG?
     }
 }
 static async Task Cleanup(IDelegatingHandler handler)
 {
     try
     {
         if (handler != null)
         {
             await handler.CloseAsync().ConfigureAwait(false);
         }
     }
     catch (Exception ex) when(!ex.IsFatal())
     {
         if (Logging.IsEnabled)
         {
             Logging.Error(handler, $"Unexpected exception: {ex}", $"{nameof(ErrorDelegatingHandler)}.{nameof(Cleanup)}");
         }
     }
 }