Flush in netty event loop

src/main/java/net/minestom/server/network/player/NettyPlayerConnection.java

@@ -71,10 +71,12 @@ public class NettyPlayerConnection extends PlayerConnection {
     @Override
     public void update() {
         // Flush
+        this.channel.eventLoop().submit(() -> {
             if (channel.isActive()) {
                 writeWaitingPackets();
                 this.channel.flush();
             }
+        });
         // Network stats
         super.update();
     }