Getting the deleted configuration is still readable

[mahuaibo]

I think this is a design flaw that does not set whether to read cached data or specify the source of the returned data

    content, err := client.GetConfig(vo.ConfigParam{
        DataId: "com.hello",
        Group:  "marx"})

    fmt.Println(content, err)

out: 2019/07/02 11:26:04 [INFO] logDir:<data/nacos/log> cacheDir:</private/var/folders/w4/d_d_m03523j12lnn4ypdq90m0000gp/T/cache> hello world2

[mahuaibo]

fixed