net/http: Serve violates tls.Config immutability promise #15908
Description
From tls.Confg docs:
After one has been passed to a TLS function it must not be modified.
But calling Serve will call setupHTTP2, which calls http2ConfigureServer, which will modify the tls.Config. Since by the time you call Serve you must have already called tls.Listen, the immutability promise is broken.
I don't think anything relies on it yet, but nothing stops someone from for example caching the NextProtos in crypto/tls.Listen or something, breaking the setupHTTP2 magic.