Adjust NetworkEvent#enqueueWork to match vanilla logic

In singleplayer our packet work could get delayed until the next tick,
breaking the expectation of packet read order. Fixes that using
NetworkHooks.openGui would result in missing inventory data on the client

src/main/java/net/minecraftforge/fml/network/NetworkEvent.java

@@ -21,8 +21,6 @@ package net.minecraftforge.fml.network;
 
 import javax.annotation.Nullable;
 
-import com.google.common.util.concurrent.ListenableFuture;
-import com.google.common.util.concurrent.ListenableFutureTask;
 import io.netty.util.Attribute;
 import io.netty.util.AttributeKey;
 
@@ -37,6 +35,7 @@ import net.minecraftforge.eventbus.api.Event;
 import net.minecraftforge.fml.LogicalSidedProvider;
 
 import java.util.List;
+import java.util.concurrent.CompletableFuture;
 import java.util.function.Supplier;
 
 public class NetworkEvent extends Event
@@ -176,13 +175,16 @@ public class NetworkEvent extends Event
             return packetHandled;
         }
 
-        @SuppressWarnings("unchecked")
-        public <V> ListenableFuture<V> enqueueWork(Runnable runnable) {
-            ListenableFutureTask<V> f = ListenableFutureTask.create(runnable, null);
-
-            LogicalSidedProvider.WORKQUEUE.<ThreadTaskExecutor<?> >get(getDirection().getReceptionSide()).execute(f);
-
-            return f;
+        public CompletableFuture<Void> enqueueWork(Runnable runnable) {
+            ThreadTaskExecutor<?> executor = LogicalSidedProvider.WORKQUEUE.get(getDirection().getReceptionSide());
+            // Must check ourselves as Minecraft will sometimes delay tasks even when they are received on the client thread
+            // Same logic as ThreadTaskExecutor#runImmediately without the join
+            if (!executor.isOnExecutionThread()) {
+                return executor.func_213165_a(runnable); // Use the internal method so thread check isn't done twice
+            } else {
+                runnable.run();
+                return CompletableFuture.completedFuture(null);
+            }
         }
 
         /**