How do I use interface{} as a Struct with json? : ```
var a interface{}
a = xxStruct
json.Unmarshal(jsonData,&a)
```
The "a" become to be a map, not a struct. For java, I could do it like this:
```
Object obj = new XXObject();
String json = JSON.toJSONString(obj);
obj = JSON.parse(json,obj.getClass())
```
What should I do?