Check this: https://gist.github.com/behe/25ddd9e873f36657776f69e6d4ea8ade
And this: https://stackoverflow.com/questions/69735525/how-to-verify-jws-transaction-of-app-store-server-api-in-go
Basically you can validate it with apples root certificate.
tjerkw
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Same issue here. iOS development comes with a lot more hurdles than Android from my experience...