remove unsafe code from global config test

rearrange code from global config client

Signed-off-by: lemonhx <lemonhx@lemonhx.tech>

Author: LemonHX

client/client.go

@@ -1813,17 +1813,17 @@ func (c *client) WatchGlobalConfig(ctx context.Context) (chan []GlobalConfigItem
 				log.Error("[pd] panic in client `WatchGlobalConfig` cause by", zap.Any("error:", r))
 				return
 			}
-			close(receiver)
 		}()
 		for {
-			m, err := res.Recv()
-			if err != nil {
-				return
-			}
 			select {
 			case <-ctx.Done():
+				close(receiver)
 				return
 			default:
+				m, err := res.Recv()
+				if err != nil {
+					return
+				}
 				arr := make([]GlobalConfigItem, len(m.Changes))
 				for j, i := range m.Changes {
 					arr[j] = GlobalConfigItem{i.GetName(), i.GetValue(), nil}

tests/server/global_config/global_config_test.go

@@ -16,11 +16,9 @@ package global_config_test
 
 import (
 	"context"
-	"reflect"
 	"strconv"
 	"testing"
 	"time"
-	"unsafe"
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/kvproto/pkg/pdpb"
@@ -201,20 +199,9 @@ func (s *GlobalConfigTestSuite) TestClientWatchCloseReceiverExternally(c *C) {
 }
 
 func (s *GlobalConfigTestSuite) TestClientWatchTimeout(c *C) {
-	ctx, _ := context.WithTimeout(s.server.Context(), time.Second)
+	ctx, cancel := context.WithCancel(s.server.Context())
 	wc, _ := s.client.WatchGlobalConfig(ctx)
-	time.Sleep(2 * time.Second)
-	closed := func(ch interface{}) bool {
-		if reflect.TypeOf(ch).Kind() != reflect.Chan {
-			panic("only channels!")
-		}
-		cptr := *(*uintptr)(unsafe.Pointer(
-			unsafe.Pointer(uintptr(unsafe.Pointer(&ch)) + unsafe.Sizeof(uint(0))),
-		))
-		cptr += unsafe.Sizeof(uint(0)) * 2
-		cptr += unsafe.Sizeof(unsafe.Pointer(uintptr(0)))
-		cptr += unsafe.Sizeof(uint16(0))
-		return *(*uint32)(unsafe.Pointer(cptr)) > 0
-	}(wc)
-	c.Assert(closed, Equals, true)
+	cancel()
+	_, opened := <-wc
+	c.Assert(opened, Equals, false)
 }