I assume those genuinly new libraries will take some time. Go is over 3 years old and yet there is hardly anything available for Go that is not available for other languages.

In fact the only things that come to my mind are vitess and Skynet - Terminator-future with Go. Being no expert in these areas, I bet there are C equalivalents that perform equally well. Also the vitess equivalent's implementation might be more complex in case it exists.

Because a library written in Go will only be useful in Go (a major shortcoming of Go) and Go can use C libraries, I suspect Go will not be used for library creation for the foreseeable future.

>Because a library written in Go will only be useful in Go (a major shortcoming of Go)

I claim that C, C++ and Java are the only languages whose libraries are heavily used from other languages. For other languages it's often better to interface via some kind of Network socket.

Surely there are Go libraries like there are Ruby libraries. But which C user seriously would want to interface a Ruby library?

Long story short: this is why Go code does not need to be called from C. :-) Different story in 5 years, in case Go is then sufficiently widespread.