How to exit a go program honoring deferred calls?

Question

I need to use defer to free allocations manually created using C library, but I also need to os.Exit with non 0 status at some point. The

Answer 1

After some research, refer to this this, I found an alternative that:

• Doesn't impose a certain architecture like in https://stackoverflow.com/a/27629493/438563
• Doesn't require any global value like in https://stackoverflow.com/a/24601700/438563

We can take advantage of panic and recover. It turns out that panic, by nature, will honor defer calls but will also always exit with non 0 status code and dump a stack trace. The trick is that we can override last aspect of panic behavior with:

package main

import "fmt"
import "os"

type Exit struct{ Code int }

// exit code handler
func handleExit() {
    if e := recover(); e != nil {
        if exit, ok := e.(Exit); ok == true {
            os.Exit(exit.Code)
        }
        panic(e) // not an Exit, bubble up
    }
}

Now, to exit a program at any point and still preserve any declared defer instruction we just need to emit an Exit type:

func main() {
    defer handleExit() // plug the exit handler
    defer fmt.Println("cleaning...")
    panic(Exit{3}) // 3 is the exit code
}

It doesn't require any refactoring apart from plugging a line inside func main:

func main() {
    defer handleExit()
    // ready to go
}

This scales pretty well with larger code bases so I'll leave it available for scrutinization. Hope it helps.

Playground: http://play.golang.org/p/4tyWwhcX0-