Spawning Gameobjects from Host and Client done right

Hey,
I try to spawn GameObjects from Clients and also from my Host. For that i use the following Code, which is attached to each Player.

[Command]
public void Cmd_SpawnUnit(string go_Name, Vector3 pos)
{

   GameObject go = Instantiate((Resources.Load(go_Name, typeof(GameObject))) as GameObject);
   go.transform.position = pos;
   NetworkServer.SpawnWithClientAuthority(go, gameObject); }
}

i call this Methode from the Player to spawn my GO´s. the Problem is that if i call the methode from the client it spawns double the ammount of objects than it should. It seems like the client is spawning the host´s again too. I allso get this Warning : Trying to send command for object without authority.

thanks for your Help

Try

NetworkServer.Spawn(go);

instead of

NetworkServer.SpawnWithClientAuthority(go, gameObject);

Spawning with Client Authority is causing those warnings.