login-validator: add signal handling

pkg/login-validator/cmd/main.go

@@ -1,10 +1,15 @@
 package main
 
 import (
+	"context"
 	"flag"
+	"fmt"
 	"log"
 	"net/http"
+	"os"
+	"os/signal"
 	"path/filepath"
+	"syscall"
 )
 
 var tftpDir string
@@ -42,6 +47,16 @@ func main() {
 		log.Fatal(err)
 	}
 
+	// Prepare graceful shutdown
+	interrupt := make(chan os.Signal, 1)
+	signal.Notify(interrupt, os.Interrupt, syscall.SIGHUP)
+	signal.Notify(interrupt, os.Interrupt, syscall.SIGTERM)
+	signal.Notify(interrupt, os.Interrupt, syscall.SIGINT)
+
+	srv := &http.Server{
+		Addr: *bind,
+	}
+
 	log.Println("Registering handlers...")
 	mux := http.NewServeMux()
 	mux.HandleFunc("/", Index)
@@ -49,6 +64,28 @@ func main() {
 	mux.HandleFunc("/logout", logout)
 	http.HandleFunc("/", mux.ServeHTTP)
 
-	log.Println("Ready, listening on port", *bind)
-	http.ListenAndServe(*bind, nil)
+	// Serve content
+	go func() {
+		log.Fatal(srv.ListenAndServe())
+	}()
+	log.Println(fmt.Sprintf("Ready, listening on %s", *bind))
+
+	// Wait shutdown signal
+	mloop: for {
+		switch <-interrupt {
+		case syscall.SIGHUP:
+			log.Println("Reloading students files...")
+			if lc.students, err = readStudentsList(studentsFile); err != nil {
+				log.Println("Error during students.csv reload:", err)
+			}
+		case syscall.SIGTERM:
+			break mloop;
+		case syscall.SIGINT:
+			break mloop;
+		}
+	}
+
+	log.Print("The service is shutting down...")
+	srv.Shutdown(context.Background())
+	log.Println("done")
 }