How to sign using a smart card

[DVSoftware]

Hi,
I'm currently using crypto11 module to login to client certificate protected API, which uses a smartcard to authenticate.
I wanted to get rid of crypto11 module and OpenSC dependency, and I stumbled upon your module, however I cannot figure out how to use the context i created with the smart card provider, because all encrypt functions create their own context. I guess i could fork the library to do it, but it would be nice to be able to supply your own context.
Also, consider implementing standard crypto.Signer interface, which would allow it to be used with TLS client directly.