Trying to improve the 'cleanup' of classpath listeners

headless-services/spring-boot-language-server/src/main/java/org/springframework/ide/vscode/boot/jdt/ls/JdtLsProjectCache.java

@@ -76,7 +76,7 @@ public class JdtLsProjectCache implements JavaProjectFinder, ProjectObserver {
 			}))
 		);
 		this.server.onShutdown(() -> 
-			disposable.thenAccept(Disposable::dispose)
+			disposable.thenAccept(Disposable::dispose).join()
 		);
 	}