[go-nuts] x/text/encoding API change caused breakage

According to the official documentation, https://github.com/golang/go/wiki/SubRepositories, the golang.org/x repos are not required to satisfy any compatibility guarantee that the Go core does. Thus, as the name suggests, these experimental repos might have their API broken every now and then if needed.
So, while frustrating as it might be for you as end-user, the mistake is on your side, for considering/assuming that they are covered by any sorts of strong guarantees instead of look at the docs / Google searching. P.S. Heads-up, there are packages in Go itself that are stil not covered by the official compatibility promise :-)