Problem applying rigidibody2d via Javascript

Hi everyone, I'm trying to add the Rigidbody2D to a set of gmeobject with a defined tag. The tag works fine and the go.transform.position as the go names are good but the rigidbody2D doesn't apply. Does anyone knows why. Thank You! Daniele

     var gos : GameObject[];
 gos = GameObject.FindGameObjectsWithTag("scelta");
 for (var go in gos){
     print(go);
     print(go.transform.position);
     var rb : Rigidbody2D = go.gameObject.AddComponent(Rigidbody2D);
     }