Wait for graceful exit.. [k8s, pod, cli]

exit.go

/*
Waits for a terminate | interrupt signal, ctrl-c before finishing main

when creating services and adapters, I like to return a cleanup function that is deferred for
each service, thus when the app closes they are teared down in reverse order.

graceful.Exit() returns two functions:

  - waitFor - which is called as the last statement of main. This will block until a signal to terminate or interrupt the executable.
  - deferMe - defer this first before the service cleanups. This ensures thar stdout/err are flushed and sleeps 1 second before exiting.

usage:

	func main() {
		waitFor, deferMe := graceful.Exit()
		defer deferMe()

		cleanupS1 := service1()
		defer cleanupS1
		...
		cleanupSx := serviceX()
		defer cleanupSx

		waitFor()
	}
*/
package graceful

import (
	"fmt"
	"os"
	"os/signal"
	"syscall"
	"time"
)

// Exit returns two functions, waitFor will block until a terminate/interrupt signal is received, deferMe will flush std streams and delay termination
// see package for example usage.
func Exit() (waitFor func(), deferMe func()) {
	signalCh := make(chan os.Signal, 1)
	signal.Notify(signalCh, syscall.SIGINT, syscall.SIGTERM)

	return func() {
			sType := <-signalCh // wait for a signal
			fmt.Printf("\n>> %s received, shutting down...\n", sType)
		}, func() {
			// make sure logs are flushed etc
			os.Stdout.Sync()
			os.Stderr.Sync()
			time.Sleep(1 * time.Second)
		}
}