doc(graceful-shutdown): failure to ListenAndServe should be a reason to exit (#1287)

Signed-off-by: Romain Beuque <romain.beuque@gmail.com>

README.md

@@ -1324,8 +1324,8 @@ func main() {
 
 	go func() {
 		// service connections
-		if err := srv.ListenAndServe(); err != nil {
-			log.Printf("listen: %s\n", err)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("listen: %s\n", err)
 		}
 	}()
 

examples/graceful-shutdown/graceful-shutdown/server.go

@@ -27,8 +27,8 @@ func main() {
 
 	go func() {
 		// service connections
-		if err := srv.ListenAndServe(); err != nil {
-			log.Printf("listen: %s\n", err)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("listen: %s\n", err)
 		}
 	}()