api_struct.go

package lib

type StockQuoteResponse struct {
  Metadata ResponseMetadata `json:"Meta Data"`
  BatchQuote BatchQuoteResponse `json:"Stock Batch Quotes"`
}

type ResponseMetadata struct {
  Information string `json:"1. Information"`
  Notes       string `json:"2. Notes"`
  TimeZone    string `json:"3. Time Zone"`
}

type BatchQuoteResponse struct {
  Quotes []StockQuote `json:"Stock Batch Quotes"`
}

type StockQuote struct {
  Symbol    string `json:"1. symbol"`
  Open      string `json:"2. open"`
  High      string `json:"3. high"`
  Low       string `json:"4. low"`
  Price     string `json:"5. price"`
  Volume    string `json:"6. volume"`
  Last_TS   string `json:"7. timestamp"`
  Currency  string `json:"8. currency"`
}

main.go

package main

import (
  "encoding/json"
  "fmt"
  "net/http"
  "os"
  "time"
  "github.com/yeukhon/stock-quote/lib"
)

var API_KEY string = os.Getenv("ALPHA_ADVANTAGE_API_KEY")
var QUOTE_URL string = "https://www.alphavantage.co/query?function=BATCH_QUOTES_US&symbols=MSFT,FB,NFLX,AMZN,IQ&apikey=" + API_KEY

// Modified from the https://stackoverflow.com/questions/17156371
var client = &http.Client{Timeout: time.Second * 5}
func getQuote(url string, target interface{}) error {
    r, err := client.Get(url)
    if err != nil {
        return err
    }
    defer r.Body.Close()
    return json.NewDecoder(r.Body).Decode(target)
}

func main() {
  stock_quote := new(lib.StockQuoteResponse)
  getQuote(QUOTE_URL, stock_quote)
  fmt.Println(stock_quote)
}

Okay, so I took some advice, and tried to catch error, not sure if I am doing right:

  stock_quote := new(lib.StockQuoteResponse)
  r := getQuote(QUOTE_URL, stock_quote)
  if r != nil {
    panic(r)
  }
  fmt.Println(stock_quote)
}

Now I got

John-Wong:stock-quote jwong$ go run main.go
panic: json: cannot unmarshal array into Go struct field StockQuoteResponse.Stock Batch Quotes of type lib.BatchQuoteResponse

goroutine 1 [running]:
main.main()
	/Users/jwong/yeukhon/git/stock-quote/main.go:30 +0xd3
exit status 2