Since your goose is low in calcium right now you might want to read this
https://learnpoultry.com/chickens-eat-spinach/
I typed in should egg layers eat spinach and since geese are egg layers I'd say this goes for all poultry.
Tube feeding would help a lot a vet can help you get started or if you can get the supplies yourself we have the info, https://www.backyardchickens.com/threads/tube-feeding-ducks-updated-5-7-2020.1211994/ tube feeding can help get them stabilized until they are able to eat on their own. Please...