Throw OperationCanceledException. Fixes #931

Author: bgrainger

src/MySqlConnector/MySqlConnection.cs

@@ -419,6 +419,7 @@ internal async Task OpenAsync(IOBehavior? ioBehavior, CancellationToken cancella
 			catch (MySqlException)
 			{
 				SetState(ConnectionState.Closed);
+				cancellationToken.ThrowIfCancellationRequested();
 				throw;
 			}
 			catch (SocketException ex)

tests/SideBySide/ConnectAsync.cs

@@ -145,9 +145,11 @@ public async Task ConnectTimeoutAsyncCancellationToken()
 			using var connection = new MySqlConnection(csb.ConnectionString);
 			var stopwatch = Stopwatch.StartNew();
 			using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(2));
-			var ex = await Assert.ThrowsAsync<MySqlException>(async () => await connection.OpenAsync(cts.Token));
+			var task = connection.OpenAsync(cts.Token);
+			var ex = await Assert.ThrowsAsync<OperationCanceledException>(async () => await task);
 			stopwatch.Stop();
-			Assert.Equal((int) MySqlErrorCode.UnableToConnectToHost, ex.Number);
+			Assert.Equal(TaskStatus.Canceled, task.Status);
+			Assert.Equal(cts.Token, ex.CancellationToken);
 			TestUtilities.AssertDuration(stopwatch, 1900, 1500);
 		}