// performed later in a program's execution, usually for

// purposes of cleanup. `defer` is often used where e.g.

// `ensure` and `finally` would be used in other languages.

​

package main

​

import "fmt"

import "os"

​

// Suppose we wanted to create a file, write to it,

// and then close when we're done. Here's how we could

// do that with `defer`.

func main() {

​

    // Immediately after getting a file object with

    // `createFile`, we defer the closing of that file

    // with `closeFile`. This will be executed at the end

    // of the enclosing function (`main`), after

    // `writeFile` has finished.

    f := createFile("/tmp/defer.txt")

    defer closeFile(f)

    writeFile(f)

}

​

func createFile(p string) *os.File {

    fmt.Println("creating")

    f, err := os.Create(p)

    if err != nil {

        panic(err)

    }

    return f

}

​

func writeFile(f *os.File) {

    fmt.Println("writing")

    fmt.Fprintln(f, "data")

​

}

​

func closeFile(f *os.File) {

    fmt.Println("closing")

    f.Close()

}

​