[go-nuts] Protocol Buffers and Go interface

Hi all, hope you guys can give me some advices!

I have a service for sending mail, every time a given a JSON message and a
Go template it generate a HTML mail and send it.
Things pretty simple with JSON since I can use a *map[string]interface{}*
to work with Go template, the service can keep running on the future
without the need to know message scheme.

Now I would like to use Google protobuf for the performance, but after
checking the *.proto file syntax(v2), their is no support for something
liek Go *map[string]interface{}*.
I have checking out proto3, they have support for map<string, string> but
It still not exactly what I need (and proto 3 still in alpha, not sure if
other language dirver support it).

Any suggesstion?
Thanks!