我试着从下面的代码中理解，我怎样才能只打印“种类”和“宽度”键值。

package main

import (
    "encoding/json"
    "fmt"
)

type Dimensions struct {
    Height int
    Width  int
}

type Bird struct {
    Species     string
    Description string
    Dimensions  Dimensions
}

func main() {
    birdJson := `{"species":"pigeon","description":"likes to perch on rocks", "dimensions":{"height":24,"width":10}}`
    var bird Bird
    json.Unmarshal([]byte(birdJson), &bird)
    fmt.Println(bird)
    // {pigeon likes to perch on rocks {24 10}}
}

我期望的输出是：鸽子和10只