Method setupSSLClientCertificates uses uses getpwuid_r (via user.Current) to find the user's home directory.

        // Automatically load certificates from ~/.postgresql.
        user, err := user.Current()
        if err != nil {
            // user.Current() might fail when cross-compiling.  We have to
            // ignore the error and continue without client certificates, since
            // we wouldn't know where to load them from.
            return
        }

It would be better to use the environment variable HOME (or, on windows, a combination of HOMEDRIVE and HOMEPATH). That way the user can control where it looks.

Avoiding os/user would also prevent having to call into cgo, which would make cross compiling a bit easier and behave more consistently. For example, the comment above about how the lookup "might fail" would no longer be necessary.

If this sounds ok, I'll send a patch.