如何解决此程序中打印出的JSON数据？

Question

I am trying to convert data through api url into JSON data. As a whole it works, but when I want to get specific data set from JSON (here I am trying MyStruct which is a data set having name, duration, listners), so it comes with blank result. On the other side, same problem with html template which does not give any result when I call it through local host port. I have declared a global instance to call data set in template function (could also use in my get content function though) but having fail result. I am wondered why data variable in get_content having blank result?

// created structurs example
type MyStruct struct {
    Name       string
    Duration   string
    and so on..
}
var data1 MyStruct

// function to retreive api data & convert into json.
func get_content() {
    // json data
    url := "http://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&api_key=c1572082105bd40d247836b5c1819623&format=json&country=Netherlands"
    url += "" // limit data for testing
    res, err := http.Get(url)
    if err != nil {
        panic(err.Error())
    }
    body, err := ioutil.ReadAll(res.Body)
    if err != nil {
        panic(err.Error())
    }

    var data MyStruct
    err = json.Unmarshal(body, &data)
    if err != nil {
        panic(err.Error())
    }
    fmt.Printf("Results: %v
", data)
}

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        get_content()
    })

    http.HandleFunc("/", template1)
    http.ListenAndServe(":8080", nil)

}

func template1(w http.ResponseWriter, r *http.Request) {

    fp := path.Join("index.html")
    tmpl, err := template.ParseFiles(fp)
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    if err := tmpl.Execute(w, data1); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
    }
}

on index file I have written names to call the data:

{{.Name}}
{{.Duration}}
{{.Listeners}}

Answer 1

To be a bit more explicit, the go data structure must match the json data structure. Not just the individual 'track', but the entire json structure.

Here's an example based on the response from the url you gave. The response is reduced to fit here, the full response is on the Playground.

The names returned by the json structure are misleading, but it's workable.

package main

import (
    "encoding/json"
    "fmt"
    "log"
)

type Track struct {
    Name     string `json:"name"`
    Duration string `json:"duration"`
    //... etc
}

type Data struct {
    Content struct {
        Tracks []Track `json:"track"`
    } `json:"tracks"`
}

func main() {
    var body = []byte(`{
        "tracks":{
            "track":[
                {
                    "name":"Hello",
                    "duration":"123",
                    "listeners":"373721",
                    "mbid":""
                }
            ]
        }
    }`)

    var data Data
    err := json.Unmarshal(body, &data)
    if err != nil {
        log.Fatal(err)
    }

    for _, track := range data.Content.Tracks {
        fmt.Printf("Track: %s
", track.Name)
    }
}

Replacing body with the full json (eg, from the url response) and running this prints:

Track: Hello Track: Can't Feel My Face Track: Sultans of Swing Track: Sorry Track: Lean On (feat. MØ & DJ Snake) Track: The Less I Know the Better Track: Africa ...