GameObject goPrefabs1= (GameObject)downloadAsset.assetBundle.Load("Prefabs_SelfRotationCube");
改为
GameObject goPrefabs1 = (GameObject)downloadAsset.assetBundle.LoadAsset("Prefabs_SelfRotationCube");
AssetBundleRequest request = assetbundle. LoadAsync(name, type);
改为
AssetBundleRequest request = assetbundle.LoadAssetAsync(name, type);