package main

import (
	"io/ioutil"
	"log"
)

func main() {
	// Read the content
	content, err := ioutil.ReadFile("hello.txt")

	if err != nil {
		log.Fatalf("error while reading the file. %v", err)
	}

	//  new content
	newText := []byte("\nAppended text.")

	// The 3 dots after newText... is a variadic argument. In simple terms it will extract all the array elements.
	// if a = [1,2,3,4]
	// func (a...) => func (1, 2, 3, 4)
	// append the content
	content = append(content, newText...)

	// overwrite the content of hello.txt
	err = ioutil.WriteFile("hello.txt", content, 0777)

	if err != nil {
		log.Fatalf("error while writing the file. %v", err)
	}
}