Godot 3.3.2 update Mutex::create removed
Using source https://downloads.tuxfamily.org/godotengine/3.3.2/ godot-3.3.2-stable.tar.xz file
edit futari_server.cpp line 137 to
mut = new Mutex();
edit futari_material.cpp line 62 to
material_mutex = new Mutex();