main.go

package main

import (
	"errors"

	"github.com/codegangsta/cli"
)

var e error

func main() {
	app := cli.NewApp()
	app.Name = "boom"
	app.Usage = "make an explosive entrance"
	app.Action = func(c *cli.Context) {
		println("boom! I say!")
		e = errors.New("I brokes it")
		return
	}
	app.After = func(c *cli.Context) error {
		return e
	}

	app.RunAndExitOnError()
}

out.sh

$ go run main.go
boom! I say!
I brokes it
exit status 1