json/call.go
func CallSC(ctx Context, sc *tchannel.SubChannel, method string, arg, resp interface{}) error {
	call, err := sc.BeginCall(ctx, method, &tchannel.CallOptions{Format: tchannel.JSON})
	if err != nil {
		return err
	}

	return wrapCall(ctx, call, method, arg, resp)
}
func CallSC(ctx Context, sc *tchannel.SubChannel, method string, arg, resp interface{}) error {
	call, err := sc.BeginCall(ctx, method, &tchannel.CallOptions{Format: tchannel.JSON})
	if err != nil {
		return err
	}

	return wrapCall(ctx, call, method, arg, resp)
}
// CallSC makes a JSON call using the given subchannel.