How to modify a return json - json

Question

I'm taking the data from the github API with golang, however, I want to send to the front only the necessary data (id, name, url, language and description) instead of just returning everything that the github API gives me.
func GetAllReposStars(w http.ResponseWriter, r *http.Request) {
enableCors(&w)
params := mux.Vars(r)
username := params["username"]
res, err := http.Get("https://api.github.com/users/" + username + "/starred")
body, err := ioutil.ReadAll(res.Body)
res.Body.Close()
if err != nil {
log.Fatal(err)
}
log.Printf("Body: %s\n", body)
if err != nil {
log.Fatal(err)
}
w.Header().Set("Content-Type", "application/json")
w.Write(body)
json.NewEncoder(w)
}

Answer 1

You can define a type that has only the keys you need and decode the response from the GitHub API into a variable of that type so that only the keys you need are kept, then write that variable to the response.
For example:
package main
import (
"encoding/json"
"log"
"net/http"
"github.com/gorilla/mux"
)
type RelevantRepoData struct {
Id int `json:"id"`
Name string `json:"name"`
Url string `json:"url"`
Language string `json:"language"`
Description string `json:"description"`
}
func GetAllReposStars(w http.ResponseWriter, r *http.Request) {
enableCors(&w)
params := mux.Vars(r)
username := params["username"]
res, err := http.Get("https://api.github.com/users/" + username + "/starred")
var repoData RelevantRepoData
err = json.NewDecoder(res.Body).Decode(&repoData)
if err != nil {
log.Fatal(err)
}
w.Header().Set("Content-Type", "application/json")
json.NewEncoder(w).Encode(repoData)
}

Answer 2

If you want to send some specific fields to front-end but in future want to handle them on backend, you can use json:"-" in your struct
e.g :
type RelevantRepoData struct {
Irrelevant string `json:"-"`
Id int `json:"id"`
Name string `json:"name"`
Url string `json:"url"`
Language string `json:"language"`
Description string `json:"description"`
}
When you return this object, the fields with json:"-" will be ignored but you can still use them on backend.