Fetch current bitcoin prices with Go.

gistfile1.go

package main

import (
    "fmt"
    "net/http"
    "io/ioutil"
    "encoding/json"
)

const baseUrl = "http://data.mtgox.com/api/2/%s/money/ticker"


// Available currencies

type Currency struct {
    Name string
    Symbol string
}

var currencies = []Currency{
    {"BTCUSD", "$"},
    {"BTCEUR", "€"},
}


// API response types

type ApiResponse struct {
    Result string
    Data DataItem
}

type DataItem struct {
    High CurrencyInfo
    Low CurrencyInfo
    Avg CurrencyInfo
    Last CurrencyInfo
}

type CurrencyInfo struct {
    Value float32 `json:",string"`
    Display string
    Currency string
}


// Function to query API

func getMtgoxJson (url string) []byte {
    // Build HTTP request
    client := &http.Client{}
    req, err := http.NewRequest("GET", url, nil)
    if err != nil {
        panic(fmt.Sprintf("%v", err))
    }
    req.Header.Add("Accept", "application/json")

    // Send request
    resp, err := client.Do(req)
    if err != nil {
        panic(fmt.Sprintf("%v", err))
    }

    // Close response body when function returns
    defer resp.Body.Close()

    // Read body
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(fmt.Sprintf("%v", err))
    }

    return body
}


// Function to parse JSON

func parseJson (data []byte) ApiResponse {
    var resp ApiResponse
    err := json.Unmarshal(data, &resp)
    if err != nil {
        panic("Could not decode JSON.")
    }
    if resp.Result != "success" {
        panic(fmt.Sprintf("API query was not successful: %v", resp.Result))
    }
    return resp
}


// Main function

func main() {
    for _, currency := range currencies {
        url := fmt.Sprintf(baseUrl, currency.Name)
        rawData := getMtgoxJson(url)
        data := parseJson(rawData)
        fmt.Printf("1 BTC = %.2f %s\n", data.Data.Last.Value, currency.Symbol)
    }
}