Retry shutdown if we meet any error

Author: CaveNightingale

src/main/java/wearblackallday/dimthread/mixin/MinecraftDedicatedServerMixin.java

@@ -0,0 +1,18 @@
+package wearblackallday.dimthread.mixin;
+
+import net.minecraft.server.dedicated.MinecraftDedicatedServer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import wearblackallday.dimthread.util.ThreadPool;
+
+@Mixin(MinecraftDedicatedServer.class)
+public abstract class MinecraftDedicatedServerMixin extends MinecraftServerMixin {
+	@Inject(method = "exit", at = @At("HEAD"))
+	private void onExit(CallbackInfo ci) {
+		ThreadPool pool = getDimThreadPool();
+		if (pool != null)
+			pool.shutdown();
+	}
+}

src/main/java/wearblackallday/dimthread/util/ThreadPool.java

@@ -128,7 +128,8 @@ public void restart() {
 	}
 
 	public void shutdown() {
-		this.executor.shutdown();
+		if (!isShutdown())
+			this.executor.shutdown();
 	}
 
 	public boolean isShutdown() {

src/main/resources/dimthread.mixins.json

@@ -5,6 +5,7 @@
   "compatibilityLevel": "JAVA_17",
   "mixins": [
     "EntityMixin",
+    "MinecraftDedicatedServerMixin",
     "MinecraftServerMixin",
     "RedstoneWireBlockMixin",
     "ServerChunkManagerMixin",