Vfrdtyky

I'm writing a small package which does a GET request to an external API every 2 seconds. It takes the value from this request and passes it into a channel. I have made this channel available to a http.handler (chi router) which upgrades to a websocket where the front-end will grab the value in realtime. the panic error is a lot of lines but i guess the most important is this:

2018/11/14 16:47:55 http: response.WriteHeader on hijacked connection

2018/11/14 16:47:55 http: response.Write on hijacked connection

Aside from that I'm sure there is a better way of doing this. Any experienced Gophers out there have any pointers to help a noob such as myself improve this?

package currencyticker



import (

    "bitbucket.org/special/api/config"

    "encoding/json"

    "fmt"

    "github.com/go-chi/chi"

    "github.com/go-chi/render"

    "github.com/gorilla/websocket"

    "github.com/leekchan/accounting"

    "io/ioutil"

    "log"

    "math/big"

    "net/http"

    "time"

)



var (

    ac       = accounting.Accounting{Precision: 2}

    from     = "USD"

    to       = "EUR,SWK"

    url      = "https://min-api.currencyapi.com/data/price?fsym=" + from + "&tsyms=" + to

    messages = make(chan float64)

)



var wsupgrader = websocket.Upgrader{

    ReadBufferSize:  1024,

    WriteBufferSize: 1024,

    CheckOrigin: func(r *http.Request) bool {

        return true // Disable CORS for testing

    },

}



// Config - init

type Config struct {

    *config.Config

}



type result map[string]float64



// New - init the configs

func New(configuration *config.Config) *Config {

    return &Config{configuration}

}



// Routes - api urls

func (config *Config) Routes() *chi.Mux {

    router := chi.NewRouter()

    router.Use(

        render.SetContentType(render.ContentTypeHTML), // Set content-Type headers as application/json

    )

    router.Get("/", config.GetPrice) // subscribe to new tweets



    return router

}



func (config *Config) GetPrice(w http.ResponseWriter, r *http.Request) {



    conn, err := wsupgrader.Upgrade(w, r, nil)

    if err != nil {

        fmt.Println(fmt.Printf("Failed to set websocket upgrade: %+v ", err))

        return

    }



    for {

        time.Sleep(1 * time.Second)



        price := <-messages



        w, err := conn.NextWriter(websocket.TextMessage)

        if err != nil {

            fmt.Println("ws error", err)

        }

        currVal := ac.FormatMoneyBigFloat(big.NewFloat(price))



        if _, err := w.Write(byte(currVal)); err != nil {

            fmt.Printf("w.Write() returned %v", err)

        }



        w.Close()



    }



}



// start getting the price of ether as soon as they ap starts

func init() {

    go startPollingPriceAPI()

}



// Go Routine to start polling

func startPollingPriceAPI() {

    for {

        time.Sleep(2 * time.Second)

        go getPriceFromAPI()

    }

}



func getPriceFromAPI() {



    w := http.Client{

        // Timeout: time.Second * 3,

    }



    req, _ := http.NewRequest(http.MethodGet, url, nil)



    res, err := w.Do(req)



    if err != nil {

        log.Println("err getting price [req]: ", err)

    }



    body, err := ioutil.ReadAll(res.Body)



    if err != nil {

        log.Println("err getting price [io-read]: ", err)

    }



    r := result{}



    if jsonErr := json.Unmarshal(body, &r); jsonErr != nil {

        log.Println("err getting price [json]: ", jsonErr)

    }

    fmt.Println("1 Dollar = €", r["EUR"])



    messages <- r["EUR"]



}