Go vendor update

vendor/google.golang.org/protobuf/internal/impl/message.go

@@ -192,12 +192,17 @@ fieldLoop:
 
 	// Derive a mapping of oneof wrappers to fields.
 	oneofWrappers := mi.OneofWrappers
-	for _, method := range []string{"XXX_OneofFuncs", "XXX_OneofWrappers"} {
-		if fn, ok := reflect.PtrTo(t).MethodByName(method); ok {
-			for _, v := range fn.Func.Call([]reflect.Value{reflect.Zero(fn.Type.In(0))}) {
-				if vs, ok := v.Interface().([]interface{}); ok {
-					oneofWrappers = vs
-				}
+	methods := make([]reflect.Method, 0, 2)
+	if m, ok := reflect.PtrTo(t).MethodByName("XXX_OneofFuncs"); ok {
+		methods = append(methods, m)
+	}
+	if m, ok := reflect.PtrTo(t).MethodByName("XXX_OneofWrappers"); ok {
+		methods = append(methods, m)
+	}
+	for _, fn := range methods {
+		for _, v := range fn.Func.Call([]reflect.Value{reflect.Zero(fn.Type.In(0))}) {
+			if vs, ok := v.Interface().([]interface{}); ok {
+				oneofWrappers = vs
 			}
 		}
 	}