go - How do I dynamically change the struct's json tag?

Question

I have the following:

package main

import (
    "encoding/json"
    "fmt"
    "os"
    "reflect"
)

type User struct {
    ID   int64  `json:"id"`
    Name string `json:"first"` // want to change this to `json:"name"`
    tag  string `json:"-"`
    Another
}

type Another struct {
    Address string `json:"address"`
}

func (u *User) MarshalJSON() ([]byte, error) {
    value := reflect.ValueOf(*u)
    for i := 0; i < value.NumField(); i++ {
        tag := value.Type().Field(i).Tag.Get("json")
        field := value.Field(i)
        fmt.Println(tag, field)
    }
    return json.Marshal(u)
}

func main() {
        anoth := Another{"123 Jennings Street"}
    _ = json.NewEncoder(os.Stdout).Encode(
        &User{1, "Ken Jennings", "name",
             anoth},
    )
}

I am trying to json encode the struct but before I do I need to change the json key...eg the final json should look like:

{"id": 1, "name": "Ken Jennings", "address": "123 Jennings Street"}

I noticed the method for value.Type().Field(i).Tag.Get("json"), however there is no setter method. Why? and how do I get the desired json output.

Also, how do I iterate through all the fields, including the embedded struct Another?

https://play.golang.org/p/Qi8Jq_4W0t

Answer 1

Waitting for answers