With Gotalk, you can use the byte-buffer request and response functionality (instead of the JSON-encoding versions) and e.g. dec.XORKeyStream(inbuf, payload) in your handler when receiving a payload followed by enc.XORKeyStream(payload, outbuf) when responding.

You could add symmetric encryption before and after putting anything on the network, and let users turn it on with a simple setting. Here's the fun part: you could use go generators to create a local key when the package is compiled. Then you wouldn't need to embed a key, or ask the user to generate and pass in a key.