Read JSON from a file, update the content and then write it to the same file again

example.json

{"hola":"mundo","number":1}

main.go

// To run:
//
// go run main.go
//
// But first, you will need to create a json file called "example.json" with the
// following content:
//
// {"hola":"mundo", "number":1}
//
package main

import (
	"encoding/json"
	"io/ioutil"
	"log"
)

type MyStruct struct {
	Hola   string `json:"hola"`
	Number int    `json:"number"`
}

func main() {
	// Read the file
	buf, err := ioutil.ReadFile("example.json")
	if err != nil {
		log.Fatal(err)
	}

	// Unmarshal the content of buf into obj
	obj := MyStruct{}
	err = json.Unmarshal(buf, &obj)
	if err != nil {
		log.Fatal(err)
	}

	// Modify the value
	obj.Number = obj.Number + 1

	// Marshal obj
	buf, err = json.Marshal(obj)
	if err != nil {
		log.Fatal(err)
	}

	// Write the marshalled object to the file again
	err = ioutil.WriteFile("example.json", buf, 0644)
	if err != nil {
		log.Fatal(err)
	}
}