fix(config): apollo close function: useless infinite loop causes high cpu usage (#1674)

Co-authored-by: wangshaosen <wangshaosen@videopls.com>

contrib/config/apollo/watcher.go

@@ -1,6 +1,7 @@
 package apollo
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/go-kratos/kratos/v2/config"
@@ -66,11 +67,13 @@ func newWatcher(a *apollo, logger log.Logger) (config.Watcher, error) {
 	}
 
 	changeCh := make(chan []*config.KeyValue)
-	a.client.AddChangeListener(&customChangeListener{in: changeCh, logger: logger})
+	listener := &customChangeListener{in: changeCh, logger: logger}
+	a.client.AddChangeListener(listener)
 
 	return &watcher{
 		out: changeCh,
 		cancelFn: func() {
+			a.client.RemoveChangeListener(listener)
 			close(changeCh)
 		},
 	}, nil
@@ -78,7 +81,11 @@ func newWatcher(a *apollo, logger log.Logger) (config.Watcher, error) {
 
 // Next will be blocked until the Stop method is called
 func (w *watcher) Next() ([]*config.KeyValue, error) {
-	return <-w.out, nil
+	kv, ok := <-w.out
+	if !ok {
+		return nil, context.Canceled
+	}
+	return kv, nil
 }
 
 func (w *watcher) Stop() error {