求助：json的结构中有map要怎么写？

package main

import (
    "encoding/json"
    "fmt"
)

type detail struct {
    Ip      string
    NetType string
    Start   int
    End     int
}
type Config struct {
    Host  string
    Nodes map[string]detail
}

func main() {

    var config Config
    file := []byte(`{
    "host": "127.0.0.1:9090",
    "nodes":
    {
        "node_1":
        {
            "ip":"192.168.1.195:5000",
            "netType":"server",
            "start":1,
            "end":60
        }
    }
}`)
    json.Unmarshal(file, &config)
    fmt.Printf("Results: %v\n", config)
    fmt.Println(config.Nodes)
}

Results: {127.0.0.1:9090 map[node_1:{192.168.1.195:5000 server 1 60}]}
map[node_1:{192.168.1.195:5000 server 1 60}]

结果不对，求指点。