package main

import (
	"fmt"
	"os"
)

func main() {

	fmt.Println("creating")
	f, err := os.Create("/tmp/defer.txt")

	// defer the closing of the file until the surrounding function returns.
	// This ensures that the file will be closed even if there is a panic or an early return in the function.
	defer closeFile(f)

	if err != nil {
		panic(err)
	}

	//will not be called in case of a panic before
	writeFile(f)

	// closeFile will be called here due to the defer-statement, even in case of a panic before.
}

func writeFile(f *os.File) {
	fmt.Println("writing")
	fmt.Fprintln(f, "data")
}

func closeFile(f *os.File) {
	fmt.Println("closing")
	var err error
	if f != nil {
		err = f.Close()
	}
	if err != nil {
		panic(err)
	}
}