JSON decode specific field golang - json

Question

I have this simple function, which gets a JSON response from a specific URI. The function accepts the httpRequest and an interface{}, which is a pointer to the struct in which I want to unmarshal my JSON response.
func (c *Client) SendRequest(req *http.Request, v interface{}) error {
...
return json.NewDecoder(resp.Body).Decode(&v)
}
An example of JSON response is:
{
"data": {
"id": "9da7a204-544e-5fd1-9a12-61176c5d4cd8"
}
}
An example of struct is:
type User struct {
ID string `json:"id;omitempty"`
}
Now, the problem is the data object. With this object, the Decode operation fails, as the object it is not included in my struct. I would like to Decode the content of data object directly, without using a temporary struct, but I don't understand how to do it.

Answer 1

Use a struct that contains a User struct to unmarshal into. See Response struct below.
type User struct {
ID string `json:"id;omitempty"`
}
type Response struct {
Data User `json:"data"`
}
After unmarshaling if r is your Response instance you can access your User by r.Data
Since you don't know the type at compile time you can use interface{} as the type of the field too.
type Response struct {
Data interface{} `json:"data"`
}
r := Response{
Data: &User{},
}
json.NewDecoder(resp.Body).Decode(&r)
And then get your user instance by
userNew, _ := r.Data.(*User)
P.S: You have a typo on your code at json tag. Replace ; by ,