Unmarshalling JSON from the http POST request

Question

I have a simple server written in Go:

package main

import (
    "encoding/json"
    "fmt"
    "github.com/gorilla/mux"
    "io/ioutil"
    "net/http"
)

type Game struct {
    RID     string `json: "RID"`
    Country string `json: "Country"`
}

func postWaitingGames(w http.ResponseWriter, r *http.Request) {
    body, err := ioutil.ReadAll(r.Body)
    if err != nil {
        fmt.Println(err)
    }
    var game Game

    err = json.Unmarshal(body, &game)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Printf("%v\n", game)

    defer r.Body.Close()
}

func main() {
    router := mux.NewRouter()

    router.HandleFunc("/wait/", postWaitingGames).Methods("POST")

    http.ListenAndServe(":8081", router)
}

And a simple client written in Python for testing purposes. Here's the code:

import json
import requests

json_to_send = json.dumps({"RID": "8", "Country": "Australia"})

post_headers = {'Content-type': 'application/json'}
addr = "http://127.0.0.1:8081/wait/"
resp = requests.post(url=addr, json=json_to_send, headers=post_headers)
print(resp.status_code)

and everytime the client hits the server, the latter yields this error:

json: cannot unmarshal string into Go value of type main.Game

I'm aware of Handling JSON Post Request in Go

Python version == 3.4 Go version == 1.7

Thank you in advance.

score 3 · Accepted Answer · answered Jan 05 '17 at 13:23

If using requests.post()'s json argument, you must pass you Python dict, not the json-serialized version -requests will take care of calling json.dumps() on it. Here you end up having your dict serialized twice.

Also - always when using the json argument - you don't need to set the content-type header, requests will take care of this too.

score 0 · Answer 2 · answered Feb 07 '20 at 18:39

So, following some tutorials like this and this, I was getting the unmarshall error and I think you have two options using requests (when content type is JSON):

payload = {
    "userId": "so_cool_user",
}

A:

requests.post(url=srvc_url, json=payload)

B:

requests.post(url=srvc_url, data=json.dumps(payload))

Unmarshalling JSON from the http POST request

2 Answers2