https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man5/resolver.5.html

OS X allows you to add TLD specific resolver configurations. Quite popular ones are /etc/resolver/vm for local virtual machines and /etc/resolver/dev for local development purposes.

https://golang.org/src/net/dnsclient_unix.go#L231

Go seems to be hardcoded to only take /etc/resolv.conf into account on Unix platforms.