Improved the comments and one of the log messages

Improved the comments and one of the log messages to make it clearer for beginners.

graceful-shutdown/graceful-shutdown/server.go

@@ -26,28 +26,31 @@ func main() {
  Handler: router,
  }
 
+ // Initializing the server in a goroutine so that
+ // it won't block the graceful shutdown handling below
  go func() {
- // service connections
  if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
  log.Fatalf("listen: %s\n", err)
  }
  }()
 
  // Wait for interrupt signal to gracefully shutdown the server with
  // a timeout of 5 seconds.
- quit := make(chan os.Signal, 1)
+ quit := make(chan os.Signal)
  // kill (no param) default send syscall.SIGTERM
  // kill -2 is syscall.SIGINT
  // kill -9 is syscall.SIGKILL but can't be catch, so don't need add it
  signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
  <-quit
- log.Println("Shutdown Server ...")
+ log.Println("Shuting down server...")
 
+ // The context is used to inform the server it has 5 seconds to finish
+ // the request it is currently handling
  ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
  defer cancel()
  if err := srv.Shutdown(ctx); err != nil {
- log.Fatal("Server Shutdown: ", err)
+ log.Fatal("Server forced to shutdown:", err)
  }
-
+ 
  log.Println("Server exiting")
 }