better termination

app/src/main/java/chess/view/simplerender/Window.java

@@ -205,7 +205,7 @@ public class Window extends JFrame implements GameListener {
 	public void winnerIs(chess.model.Color color) {
 		SwingUtilities.invokeLater(() -> {
 			JOptionPane.showMessageDialog(this, "Victory of " + color);
-			this.dispose();
+			onGameEnd();
 		});
 	}
 
@@ -229,7 +229,7 @@ public class Window extends JFrame implements GameListener {
 	public void patSituation() {
 		SwingUtilities.invokeLater(() -> {
 			JOptionPane.showMessageDialog(this, "Pat. It's a draw!");
-			this.dispose();
+			onGameEnd();
 		});
 	}
 
@@ -240,6 +240,11 @@ public class Window extends JFrame implements GameListener {
 		});
 	}
 
+	private void onGameEnd() {
+		this.dispose();
+		this.commandExecutor.close();
+	}
+
 	@Override
 	public void gameStarted() {
 		buildBoard();