Yahoo stock simulator in GO Language

I have built a virtual stock trading system for whoever wants to learn how to invest in stocks. The system uses real-time pricing via Yahoo finance API and supports USD currency only. The system will have 2 components: Client and Server. Client: The JSON-RPC client will take command line input and send requests to the server. Server: The trading engine will have JSON-RPC interface for the below features.

Feature #1: Buying stock

1. Request

• User requests the server to buy stocks by giving the stock symbol and the percent of the budget he wants to invest in that stock.

• He/She also inputs the overall budget for this transaction.

          “stockSymbolAndPercentage”: string (E.g. “GOOG: 50%, YHOO: 50 %”)
                            “budget”: float32
  

2. Response

• Server then allocates the stock to the user after performing some validations.

• It return a tradeID, the unvested (leftover) amount and the stock details that include: Stock symbol, no of stocks purchased for that stock and the price at which the stock was bought.

                                “tradeId”: number
       “stocks”: string (E.g. “GOOG: 100:$500.25”, “YHOO: 200:$31.40”)
                            “unvestedAmount”: float32
  

Feature #2: Check portfolio (Loss/Gain)

1. Request

• User can check the portfolio to see if the current price of the stocks and to figure out if the previous transaction were a profit or loss.

• User only inputs the tradeId that was previously allocated to earlier transaction(s).

                            “tradeId”: number
  

2. Response

• User gets the details of the stocks that were purchased w.r.t the tradeId as provided.

• The details also include the (+) Profit or (-) Loss symbol that compares the current price of the stocks to earlier one along with the unvested amount.

            “stocks”: string (E.g. “GOOG:100:+$520.25”, “YHOO:200:-$30.40”)
                        “currentMarketValue” : float32
                         “unvestedAmount”: float32