Golang : Intercept Ctrl-C interrupt or kill signal and determine the signal type

Problem :

Your server needs to perform some clean up operation or flush everything in memory to disk before shutting down. How to intercept Ctrl-C,interrupt or kill signal in your program and perform the tasks? How to determine the signal type that your program received?

Solution :

Use the os/signal.Notify() function to intercept the signals and perform the required tasks before shutting down.

For example : (interrupt.go)

 package main

 import (
 "log"
 "net/http"
 "os"
 "os/signal"
 "syscall"
 )

 func SayHelloWorld(w http.ResponseWriter, r *http.Request) {
 html := `Hello 
 World!`

 w.Write([]byte(html))
 }

 func main() {
 mux := http.NewServeMux()
 mux.HandleFunc("/", SayHelloWorld)

 log.Println("Server started. Press Ctrl-C to stop server")

 // Catch the Ctrl-C and SIGTERM from kill command

 ch := make(chan os.Signal, 1)

 signal.Notify(ch, os.Interrupt, os.Kill, syscall.SIGTERM)


 go func() {
 signalType := <-ch
 signal.Stop(ch)
 log.Println("Exit command received. Exiting...")

 // this is a good place to flush everything to disk
 // before terminating.
 log.Println("Signal type : ", signalType)

 os.Exit(0)

 }()

 log.Println(http.ListenAndServe(":8080", mux))

 }

Run the code above with these commands :

>go run interrupt.go and press Ctrl-C.

2015/06/23 11:40:43 Server started. Press Ctrl-C to stop server

^C2015/06/23 11:40:45 Exit command received. Exiting...

2015/06/23 11:42:45 Signal type : interrupt

or

>go run interrupt.go & (no applicable to Windows)

You will see program goes to background. Find out the process ids with the ps -ef | grep interrupt command.

>ps -ef | grep interrupt

root 30551 30306 1 11:41 pts/0 00:00:00 go run interrupt.go

root 30559 30551 0 11:41 pts/0 00:00:00 /tmp/go-build908833771/command-line-arguments/_obj/exe/interrupt

In this example, I would issue the command

>kill 30559 30551 and a similar output will be produced except that this time, the signal type is terminated

Reference :

http://golang.org/pkg/os/signal/#Notify