Google today released Go 1.5, the sixth major stable release of its Go programming language. You can download Go 1.5 right now from the Go downloads page. This is not a major release, as denoted by the version number and the fact that the only language change is the lifting of a restriction in the map literal syntax to make them more consistent with slice literals. That said, Go 1.5 does include a significant rewrite: The compiler tool chain has been translated from C to Go. This means the last vestiges of C code have been finally removed from the Go code base.
As for actual changes in Go 1.5, you’ll want to read the full release notes. Highlights include improvements to garbage collection, the developer tools, the standard library, and new ports.