解组不带结构的未知JSON字段

Question

I am trying to unmarshal a JSON object which has an optional array, I am doing this without an array and this is what I got so far:

import (
    "encoding/json"
    "fmt"
)

func main() {

    jo := `
        {
            "given_name": "Akshay Raj",
            "name": "Akshay",
            "country": "New Zealand",
            "family_name": "Gollahalli",
            "emails": [
                "[e-mail]"
                ]
        }
        `
    var raw map[string]interface{}
    err := json.Unmarshal([]byte(jo), &raw)
    if err != nil {
        panic(err)
    }

    fmt.Println(raw["emails"][0])

}

The emails field might or might not come sometime. I know I can use struct and unmarshal it twice for with and without array. When I try to get the index 0 of raw["emails"][0] I get the following error

invalid operation: raw["emails"][0] (type interface {} does not support indexing)

Is there a way to get the index of the emails field?

Update 1

I can do something like this fmt.Println(raw["emails"].([]interface{})[0]) and it works. Is this the only way?

Answer 1

The easiest way is with a struct. There's no need to unmarshal twice.

type MyStruct struct {
    // ... other fields
    Emails []string `json:"emails"`
}

This will work, regardless of whether the JSON input contains the emails field. When it is missing, your resulting struct will just have an uninitialized Emails field.