1

I'm trying to consume JSON apis through golang, but having a terrible time getting the response back. I'm using a sample JSON endpoint http://jsonplaceholder.typicode.com/posts/1 that returns 

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
}

This is my code which comes from this Stack Overflow Answer: 

package main

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

type Post struct {
    UserID string
    ID string
    Title string
    Body string
}

func getJson(url string, target interface{}) error {
    r, err := http.Get(url)
    if err != nil {
        return err
    }
    defer r.Body.Close()
    fmt.Println(r)
    return json.NewDecoder(r.Body).Decode(target)
}

func main() {
    post := new(Post) // or &Foo{}
    getJson("http://jsonplaceholder.typicode.com/posts/1", &post)
    println(post.Body)

}

And this is the output: 

go run main.go 
&{200 OK 200 HTTP/1.1 1 1 map[Cf-Cache-Status:[HIT] Cf-Ray:[2bf857d2e55e0d91-SJC] Access-Control-Allow-Credentials:[true] Cache-Control:[public, max-age=14400] Expires:[Sat, 09 Jul 2016 06:28:31 GMT] X-Content-Type-Options:[nosniff] Server:[cloudflare-nginx] Date:[Sat, 09 Jul 2016 02:28:31 GMT] Connection:[keep-alive] X-Powered-By:[Express] Etag:[W/"124-yv65LoT2uMHrpn06wNpAcQ"] Content-Type:[application/json; charset=utf-8] Set-Cookie:[__cfduid=d0c4aacaa5db8dc73c59a530f3d7532af1468031311; expires=Sun, 09-Jul-17 02:28:31 GMT; path=/; domain=.typicode.com; HttpOnly] Pragma:[no-cache] Via:[1.1 vegur] Vary:[Accept-Encoding]] 0xc8200ee100 -1 [chunked] false map[] 0xc8200da000 <nil>}

I know the endpoint works. Is this an encoding issue or something else? I'm on Mac OSX 10.11.15.

Thanks

Community
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Tom Tunguz
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2 Answers2

3

You have error in unmarshal: cannot unmarshal number into Go value of type string if you print error. UserId and Id should be int.

Please don't ignore error!

try this code: 

package main

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

type Post struct {
    UserID int
    ID     int
    Title  string
    Body   string
}

func getJson(url string, target interface{}) error {
    r, err := http.Get(url)
    if err != nil {
        return err
    }
    defer r.Body.Close()
    fmt.Println(r)
    return json.NewDecoder(r.Body).Decode(target)
}

func main() {
    post := new(Post) // or &Foo{}
    err := getJson("http://jsonplaceholder.typicode.com/posts/1", &post)
    if err != nil {
        panic(err)
    }

    println(post.Body)
    fmt.Printf("Post: %+v\n", post)
}

Edited: Why can't I print out the contents of the response body and see it in the command line? Is it encoded? Ans: HTTP request or response used to be in a format or encoded defined by the response-header fields.

The response-body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied to ensure safe and proper transfer of the message.

If you print: fmt.Println("Header: %#v\n", r.Header)
You will see, Content-Type:[application/json; charset=utf-8] That's why you are decoding with Json. It also could be xml.

Pravin Mishra
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  • Thanks. Super helpful. Quick follow up question: why can't I print out the contents of the response body and see it in the command line? Is it encoded? – Tom Tunguz Jul 09 '16 at 03:20
0

maybe you should try this:

package main

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

type Result struct {
    UserID int    `json:"userId"`
    ID     int    `json:"id"`
    Title  string `json:"title"`
    Body   string `json:"body"`
}   

func main() {

    url := "http://jsonplaceholder.typicode.com/posts/1"

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

    res, _ := http.DefaultClient.Do(req)

    defer res.Body.Close()
    body, _ := ioutil.ReadAll(res.Body)

    var result Result
    err := json.Unmarshal(body, &result)
    if err != nil {
        fmt.Println(err)
    }   

    fmt.Println(res)
    fmt.Println(string(body))

    fmt.Println(result)
    //fmt.Println(result.Title)
    //fmt.Println(result.Body)
}

You will get a Result struct

wyiwt
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