Saving data with a REST client after consuming an external API in Go

Question

I am new to Go lang have created a REST client that consumes the alphavantage API

The JSON structure which comes up after I make a GET request looks as below. I only need the Time Series key data so that I do my own calculations. How do I get the data from the Time Series and save it so that I do my own manipulations of the data?

JSON

{
    "Meta Data": {
        "1. Information": "Intraday (1min) prices and volumes",
        "2. Symbol": "MSFT",
        "3. Last Refreshed": "2018-05-25 16:00:00",
        "4. Interval": "1min",
        "5. Output Size": "Compact",
        "6. Time Zone": "US/Eastern"
    },
    "Time Series (1min)": {
        "2018-05-25 16:00:00": {
            "1. open": "98.2700",
            "2. high": "98.4400",
            "3. low": "98.2650",
            "4. close": "98.3600",
            "5. volume": "2466507"
        }
    }
}

code for REST Client

package main

import (
    "net/http"
    "fmt"
    "io/ioutil"
    //encode and decode JSON streams
    "encoding/json"
)



func main() {
    response, err := http.Get("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=MSFT&interval=1min&apikey=demo")

    if err!=nil{
        fmt.Println(err)
        return
    }
    defer response.Body.Close()
    contents, err := ioutil.ReadAll(response.Body)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(contents))
}

Answer 1

Using an interface as suggested is a good idea, but in this case, since you know the structure of the response defining using an explicit type suffices and should be easier to work with:

package main

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

type values map[string]string
type TimeSeries struct {
    Item map[string]values `json:"Time Series (1min)"`
}

func main() {
    response, err := http.Get("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=MSFT&interval=1min&apikey=demo")

    if err != nil {
        fmt.Println(err)
        return
    }
    defer response.Body.Close()
    contents, err := ioutil.ReadAll(response.Body)
    if err != nil {
        fmt.Println(err)
        return
    }
    var ts TimeSeries
    err = json.Unmarshal(contents, &ts)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%#v", ts)
}