Go is still at 1.3 but 1.4 then recently 1.5 are now available.
Furthermore it improves overall performance (great concurrent garbage collection from 1.5), little langage change make writing and reading go code easier and quicker which is always welcome, plus standard library improvements/bugfixes, see:
https://golang.org/doc/go1.4#language
https://golang.org/doc/go1.5#language
Thanks for these great programming challenges !