Check if channels are closed in the example (#244)

* Check if channels are closed in the example

* Check if the channels are closed before printing

example_test.go

@@ -23,12 +23,18 @@ func ExampleNewWatcher() {
 	go func() {
 		for {
 			select {
-			case event := <-watcher.Events:
+			case event, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
 				log.Println("event:", event)
 				if event.Op&fsnotify.Write == fsnotify.Write {
 					log.Println("modified file:", event.Name)
 				}
-			case err := <-watcher.Errors:
+			case err, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
 				log.Println("error:", err)
 			}
 		}