Add comment to explain blocking call while migration runs

Why use a system Thread?

Dockerfile

@@ -16,7 +16,7 @@ COPY ./ui .
 RUN npm run build-only
 
 # Stage 3: Create the jlink app
-FROM docker.io/eclipse-temurin:20-jdk-alpine
+FROM docker.io/eclipse-temurin:19-jdk-alpine
 WORKDIR /app
 COPY --from=maven /app/target/dchat-*-fat.jar /app/dchat.jar
 COPY --from=vuejs /app/dist /app/ui/dist

docker-compose.yml

@@ -14,6 +14,7 @@ services:
       - POSTGRES_PASSWORD=<postgres-password>
       - POSTGRES_URL=jdbc:postgresql://db:5432/dchat
       - API_PORT=8080
+      - JDK_JAVA_OPTIONS="--enable-preview"
   db:
     image: docker.io/postgres:15-alpine
     restart: unless-stopped

src/main/java/de/hhhammer/dchat/DiscordBot.java

@@ -36,7 +36,7 @@ public class DiscordBot implements Runnable {
                 .setToken(discordApiKey)
                 .login()
                 .join();
-        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+        Runtime.getRuntime().addShutdownHook(Thread.ofVirtual().unstarted(() -> {
             logger.info("Shutting down Discord application");
             discordApi.disconnect();
         }));

src/main/java/de/hhhammer/dchat/Main.java

@@ -60,8 +60,7 @@ public class Main {
     public void run() {
         logger.info("Starting services...");
         try (var executor = Executors.newFixedThreadPool(2)) {
-            var migrationResult = executor.submit(dbMigrator);
-            migrationResult.get();
+            executor.submit(dbMigrator).get(); // Waiting for migrations
             executor.submit(discordBot);
             executor.submit(webAPI);
         } catch (ExecutionException | InterruptedException e) {