I have to add

  1. JSON-RPC2.0
  2. over websockets, to my
  3. Golang
  4. Client process

to communicate with another server. Unfortunately, none of the requirements can be changed.

I have libs and example code that offer parts of the solution but I have been unable to put it all together.

I have looked at Ethereum (I cannot find a client example) Ethereum rpc

This one looked promising but I cannot make my client work.

type Params struct {
    Name string `json:"name"`
}

func main() {
    h := NewRPCHandler()
    h.Register("some_handler", dummySuccessHandler)
    ts := http.Server{Handler: h}
    defer ts.Close()
    conn, _, err := websocket.DefaultDialer.Dial("ws://127.0.0.1:8080/ws_rpc", nil)
    if err != nil {
        log.Printf("Error dialing %v", err)
    }

    client := jsonrpc.NewClient(conn.UnderlyingConn())

    par := &Params{"newuser"}
    req, err := json.Marshal(&par)
    if err != nil {
        log.Printf("Bad marshal %#v", err)
    }
    var resp Result
    err = client.Call("some_handler", &req, &resp)

I tried with/without marshaling but I'm clutching at straws here.