Reading and writing JSON objects in Golang

making_json_with_maps.go

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	myJson := map[string]interface{}{
		"name": "Arsham",
		"age": 22,
		"male": true,
	}
	myJsonBytes, err := json.Marshal(myJson)
	if err != nil {
		fmt.Print(err)
	}
	fmt.Println(string(myJsonBytes))
}

making_json_with_structs.go

package main

import (
	"encoding/json"
	"fmt"
)

type myJsonStructure struct {
	Name string `json:"name_customized_field"` // You can customize your fields names like this.
	Age int `json:"age"`
	Male bool `json:"male"`
}

func main() {
	myJson := &myJsonStructure{"Arsham", 22, true}
	myJsonBytes, err := json.Marshal(myJson)
	if err != nil {
		fmt.Print(err)
	}
	fmt.Println(string(myJsonBytes))
}

reading_structured_json.go

// This is for times we know what we will get, actually what keys we have in our JSON.
// This is a full example including type convertions and Get request and error handeling.
package main

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

type ResponseJSON struct {
	UserID int `json:"userId"`
	ID int `json:"id"`
	Title string `json:"title"` 
	Completed bool // If the only difference is first capital C, we don't need to write `json:"completed"` 
}

func main() {
	resp, err := http.Get("https://jsonplaceholder.typicode.com/todos/1")
	if err != nil {
		fmt.Print(err)
	}
	responseByteValue, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Print(err)
	}
	defer resp.Body.Close()
	response := &ResponseJSON{}
	json.Unmarshal(responseByteValue, response)
	fmt.Printf("%s - %s - %s", response.Title, strconv.FormatBool(response.Completed), strconv.Itoa(response.UserID))
}

reading_unstructed_json.go

// This example is for times we don't know what keys we will have in our json
// Actually when json structure is kind of unknown for us
// I removed error handelings to increase simplicity, but you know where to place them.
package main

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

func main() {
	resp, _ := http.Get("https://jsonplaceholder.typicode.com/todos/1")
	responseByteValue, _ := ioutil.ReadAll(resp.Body)
	defer resp.Body.Close()
  
	var response map[string]interface{}
  json.Unmarshal([]byte(responseByteValue), &response)
  
	fmt.Printf("%+v\n", response)
  fmt.Printf("%+v\n", response["title"])
}

snippet.go

// This code won't run alone, it is just a snippet for copy/paste! or even seeing steps clearly.
import (
	"encoding/json"
	"io/ioutil"
)

type ResponseJSON struct {}

// data variable is something that implements reader interface
byteValue := ioutil.ReadAll(data)
response := &ResponseJSON{}
json.Unmarshal(responseByteValue, response)
fmt.Printf("%+v\n", response)