fix(contrib/registry/file/v2): fix the panic caused by channel closin…

…g after `resolver closed` (#3691)

contrib/registry/file/file_discovery.go

@@ -10,6 +10,7 @@ import (
 	"context"
 
 	"github.com/gogf/gf/v2/container/gmap"
+	"github.com/gogf/gf/v2/container/gtype"
 	"github.com/gogf/gf/v2/frame/g"
 	"github.com/gogf/gf/v2/net/gsvc"
 	"github.com/gogf/gf/v2/os/gfile"
@@ -55,8 +56,12 @@ func (r *Registry) Watch(ctx context.Context, key string) (watcher gsvc.Watcher,
 		prefix:    key,
 		discovery: r,
 		ch:        make(chan gsvc.Service, 100),
+		closed:    gtype.NewBool(false),
 	}
 	_, err = gfsnotify.Add(r.path, func(event *gfsnotify.Event) {
+		if fileWatcher.closed.Val() {
+			return
+		}
 		if event.IsChmod() {
 			return
 		}

contrib/registry/file/file_watcher.go

@@ -9,6 +9,8 @@ package file
 import (
 	"context"
 
+	"github.com/gogf/gf/v2/container/gtype"
+	"github.com/gogf/gf/v2/errors/gerror"
 	"github.com/gogf/gf/v2/net/gsvc"
 )
 
@@ -17,11 +19,15 @@ type Watcher struct {
 	prefix    string            // Watched prefix key, not file name prefix.
 	discovery gsvc.Discovery    // Service discovery.
 	ch        chan gsvc.Service // Changes that caused by inotify.
+	closed    *gtype.Bool       // Whether the channel has been closed
 }
 
 // Proceed proceeds watch in blocking way.
 // It returns all complete services that watched by `key` if any change.
 func (w *Watcher) Proceed() (services []gsvc.Service, err error) {
+	if w.closed.Val() {
+		return nil, gerror.New("discovery service was closed")
+	}
 	<-w.ch
 	return w.discovery.Search(context.Background(), gsvc.SearchInput{
 		Prefix: w.prefix,
@@ -30,6 +36,8 @@ func (w *Watcher) Proceed() (services []gsvc.Service, err error) {
 
 // Close closes the watcher.
 func (w *Watcher) Close() error {
-	close(w.ch)
+	if w.closed.Cas(false, true) {
+		close(w.ch)
+	}
 	return nil
 }