why OnConfigChange() not work?

[dncmn]

I write in a golang test file.code following

func TestViper(t *testing.T) {
//func main() {
viper.SetConfigName("config")
viper.AddConfigPath("../config")
viper.AddConfigPath(".")
viper.AutomaticEnv()
viper.SetConfigType("yaml")
var configuration c.Configurations

if err := viper.ReadInConfig(); err != nil {
	log.Fatal(err)
	return
}

err := viper.Unmarshal(&configuration)
if err != nil {
	log.Fatal(err)
	return
}
fmt.Println(configuration.Server.Port)
fmt.Println(configuration.GameServer)
fmt.Println(configuration.GOPATH)
fmt.Println(configuration.EXAMPLE_VAR)
viper.WatchConfig()
viper.OnConfigChange(func(in fsnotify.Event) {
	if in.Op == fsnotify.Write {
		if err := viper.Unmarshal(&configuration); err != nil {
			log.Fatal(err)
		}
		fmt.Println("write")
		log.Printf("%#v", configuration)
	}

})
select {}

}

#658 config.yaml
server:
port: 8080
gameServer:
host: http://127.0.0.1/
token: 789
GOPATH: "variable from config.yaml"
EXAMPLE_VAR: "path from config.yaml"

after run test method ,I modify token from "789" to "123456"

but I see nothing output

[dncmn]

wrong op.Name