stop DNS server properly when interrupted with ctrl+c, SIGTERM, SIGHUP or SIGQUIT

app.go

@@ -7,8 +7,10 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"strconv"
+	"syscall"
 	"time"
 
 	"github.com/gobuffalo/packr"
@@ -164,10 +166,13 @@ func main() {
 		}
 	}()
 
-	// Eat all args so that coredns can start happily
-	if len(os.Args) > 1 {
-		os.Args = os.Args[:1]
-	}
+	signal_channel := make(chan os.Signal)
+	signal.Notify(signal_channel, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP, syscall.SIGQUIT)
+	go func() {
+		<-signal_channel
+		cleanup()
+		os.Exit(0)
+	}()
 
 	// Save the updated config
 	err := config.write()
@@ -192,6 +197,13 @@ func main() {
 	log.Fatal(http.ListenAndServe(address, nil))
 }
 
+func cleanup() {
+	err := stopDNSServer()
+	if err != nil {
+		log.Printf("Couldn't stop DNS server: %s", err)
+	}
+}
+
 func getInput() (string, error) {
 	scanner := bufio.NewScanner(os.Stdin)
 	scanner.Scan()

coredns.go

@@ -74,3 +74,16 @@ func reconfigureDNSServer() error {
 
 	return nil
 }
+
+func stopDNSServer() error {
+	if !isRunning() {
+		return fmt.Errorf("Refusing to stop forwarding DNS server: not running")
+	}
+
+	err := dnsServer.Stop()
+	if err != nil {
+		return errorx.Decorate(err, "Couldn't stop forwarding DNS server")
+	}
+
+	return nil
+}