Go has a growing number of packages for things that you might want to interface with: http://go-lang.cat-v.org/pure-go-libs and http://golang.org/pkg/ There are already packages for most databases, data interchange formats, crypto, etc. that most people want to use.

Another draw of Go that you didn't mention is the language and toolchain design itself. I know Javascript better than Go, but would rather write servers in Go than JS.