Try for multiple thread

src/main/java/ch/uzh/ifi/hase/soprafs24/Application.java

@@ -5,12 +5,14 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
+import org.springframework.scheduling.annotation.EnableAsync;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.servlet.config.annotation.CorsRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 @RestController
 @SpringBootApplication
+@EnableAsync
 public class Application {
 
   public static void main(String[] args) {

src/main/java/ch/uzh/ifi/hase/soprafs24/service/GameService.java

@@ -29,6 +29,7 @@
 import ch.uzh.ifi.hase.soprafs24.repository.GameRepository;
 import ch.uzh.ifi.hase.soprafs24.repository.PlayerRepository;
 import org.springframework.http.HttpStatus;
+import org.springframework.scheduling.annotation.Async;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.server.ResponseStatusException;
@@ -121,6 +122,7 @@ public void checkIfAllReady(Room room) {
         }
     }
 
+    @Async
     public void startGame(Room room) {
         // Initialize a new game object and player objects, then save them to the
         // database