Unmarshalling nested JSON / Hash with dynamic key

app.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"os"
)

type Stock struct {
	Symbol        string  `json:"symbol"`
	Title         string  `json:"title"`
	Share         int     `json:"share"`
	PurchasePrice float64 `json:"purchase_price"`
	TargetPrice   float64 `json:"target_price"`
}
type Account map[string]Stock

func main() {
	raw, err := ioutil.ReadFile("stock.json")
	if err != nil {
		fmt.Println(err.Error())
		os.Exit(1)
	}
	var account Account
	json.Unmarshal(raw, &account)
	log.Println(account)
}

stock.json

{
  "MU": {
    "symbol": "MU",
    "title": "micro semiconductor",
    "share": 400,
    "purchase_price": 60.5,
    "target_price": 70
  },
  "LSCC":{
    "symbol": "LSCC",
    "title": "lattice semiconductor",
    "share": 200,
    "purchase_price": 20,
    "target_price": 30
  }
}