better termination

app/src/main/java/chess/controller/CommandExecutor.java

@@ -98,4 +98,7 @@ public class CommandExecutor {
 		this.game = game;
 	}
 
+	public void close() {
+		this.dispatcher.stopService();
+	}
 }

app/src/main/java/chess/controller/event/GameDispatcher.java

@@ -2,7 +2,7 @@ package chess.controller.event;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.function.Consumer;
 
@@ -12,7 +12,7 @@ import chess.model.Coordinate;
 public class GameDispatcher implements GameListener{
 
 	private final List<GameListener> listeners;
-	private final Executor executor;
+	private final ExecutorService executor;
 
 	public GameDispatcher() {
 		this.listeners = new ArrayList<>();
@@ -71,5 +71,9 @@ public class GameDispatcher implements GameListener{
 	public void updateDisplay() {
 		asyncForEachCall((l) -> l.updateDisplay());
 	}
-	
+
+	public void stopService() {
+		this.executor.shutdown();
+	}
+
 }