As of right now you can't use the built in net/http to connect to hostnames, check this issue.
There are few workarounds you could use.
generate /etc/resolv.conf on your program start if you have root access, ugly but easy and simple.
store resolv.conf somewhere and patch http://golang.org/src/pkg/net/dnsclient_unix.go#L169 to use that custom path.
$GOROOT/src/pkg/net/dnsconfig_unix.goto get the nameservers by executing
implement the full patch at https://gist.github.com/ernesto-jimenez/8042366