There have been many changes to both the Go language and the stdlib, but it is really easy to keep your code updated (specially since gofix was introduced: http://blog.golang.org/2011/04/introducing-gofix.html ) so this should not be an obstacle to learning the language.
That said, version "1" of the language is due for early next year, which should provide a long-term stable language and set of libraries, for details see: