A goose without one wing may not fly and I know it's wild and that it's it only defence but a goose with one wing can still swim and will always stay on that lake or river so you can see it every day
It might be more open to predators but you can be proud you helped him every time you see him.
Reason I'm saying this is because there is a greylag(another wild breed)gander with one wing in a lake near me and a vet helped him for whatever happened to that wing and him and two others stay with eachother over the winter.
But if his broken wing is badly infected or in a very bad state he is best to be put down but look at the information Miss Lydia gave you first!