`undefined: keychain.NewItem` when building for Linux from macOS

[MuweiHe]

Hello! I see Linux support is mentioned in readme, but when I try to build for Linux, I'm seeing many undefined errors. Is Linux support official? Thank you!

Saw a few other discussions using xgo: https://github.com/karalabe/xgo, and using different build files for different os: https://github.com/keybase/go-keychain/issues/14. Is this package only meant to be called in darwin, and not supposed to be called in other os? How to make it work like mentioned in readme, communicates to a provider of the DBUS SecretService spec like gnome-keyring or ksecretservice.?