Allow cancellation to propagate

src/Microsoft.Extensions.Diagnostics.HealthChecks/DefaultHealthCheckService.cs

@@ -77,7 +77,9 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
 
                             Log.HealthCheckEnd(_logger, registration, entry, stopwatch.GetElapsedTime());
                         }
-                        catch (Exception ex)
+
+                        // Allow cancellation to propagate.
+                        catch (Exception ex) when (ex as OperationCanceledException == null)
                         {
                             entry = new HealthReportEntry(HealthStatus.Failed, ex.Message, ex, data: null);
                             Log.HealthCheckError(_logger, registration, ex, stopwatch.GetElapsedTime());

test/Microsoft.Extensions.Diagnostics.HealthChecks.Tests/DefaultHealthCheckServiceTest.cs

@@ -188,6 +188,35 @@ namespace Microsoft.Extensions.Diagnostics.HealthChecks
                 });
         }
 
+        [Fact]
+        public async Task CheckHealthAsync_Cancellation_CanPropagate()
+        {
+            // Arrange
+            var insideCheck = new TaskCompletionSource<object>();
+
+            var service = CreateHealthChecksService(b =>
+            {
+                b.AddAsyncCheck("cancels", async ct =>
+                {
+                    insideCheck.SetResult(null);
+
+                    await Task.Delay(10000, ct);
+                    return HealthCheckResult.Failed();
+                });
+            });
+
+            var cancel = new CancellationTokenSource();
+            var task = service.CheckHealthAsync(cancel.Token);
+
+            // After this returns we know the check has started
+            await insideCheck.Task;
+
+            cancel.Cancel();
+
+            // Act & Assert
+            await Assert.ThrowsAsync<TaskCanceledException>(async () => await task);
+        }
+
         [Fact]
         public async Task CheckHealthAsync_ConvertsExceptionInHealthCheckToFailedResultAsync()
         {