How can I user struct and interface to get different json construction in Golang

Question

It can gets different json construction:

type 1:

{"errcode": 0, "errmsg": "OK", "data": {"name": "Jolly", "age": 19}}

type 2:

{"errcode": 0, "errmsg": "OK", "data": {"friend": "Lisa", "country": "US"}}

I knew I can get those by define 4 structs like:

type Base1 struct {
    ErrCode int    `json:"errcode"`
    ErrMsg  string `json:"errmsg"`
    Data    Person `json:"data"`
}
type Person struct {
    Age   int    `json:"age"`
    Name  string `json:"name"`
}

and

type Base2 struct {
    ErrCode int    `json:"errcode"`
    ErrMsg  string `json:"errmsg"`
    Data    Info   `json:"data"`
}
type Info struct {
    Friend   string    `json:"friend"`
    Country  string    `json:"country"`
}

If I want to load json 1, just type data := Base1{}

If I want to load json 2, just type data := Base2{}

But I want to know how can I get them by 3 structs and using interface, because I have lots of APIs that provide json construction, their first layer all same as struct Base

like

type Base struct {
    ErrCode int         `json:"errcode"`
    ErrMsg  string      `json:"errmsg"`
    Data    interface   `json:"data"`
}

How to write the data := Base{...} and let it become struct Base1, Base2