The way to do streaming JSON parsing is with a Decoder:
json.NewDecoder(resp.Body).Decode(&yourStuff)
For a streaming API where it's a bunch of objects coming back (a la Twitter), that should stream great with this model and the built-in encoding/json API. But if it's a large response where you have an object that's got a giant array with 10MB of stuff, you probably need to write your own Decoder to pull those inner pieces out and return them. I'm running into that problem with a library I've written.