gorilla/rpc — pull request #18 by rjeczalik (2013-09-24 22:27:12+00:00)
Title: json.WriteError: result field must be null

According to JSON-RPC spec only one of error and result fields can be non-null. Besides json.DecodeClientResponse would fail on attempt of unmarshaling {"error_message":"..."} to user-defined reply value - current implementation have hidden that problem.