go语言读取json并下载高清妹子图片

package main
import (
  "fmt"
  "io"
  "io/ioutil"
  "net/http"
  "os"
  "path/filepath"
  "strconv"
  //"encoding/json"
  "strings"
  "github.com/bitly/go-simplejson"
)
const (
  DataRoot   = "./tmp/" // 存放封面图的根目录
  TimeoutLimit = 10    // 设置超时时间
  PageUrl   = "http://api.lovebizhi.com/macos_v4.php"
)
// 壁纸类型，有编号，长宽和URL
type Wallpaper struct {
  Pid   int
  Url   string
  Width  int
  Height  int
}
// 将图片下载并保存到本地
func SaveImage(paper *Wallpaper) {
  res, err := http.Get(paper.Url)
  defer res.Body.Close()
  if err != nil {
    fmt.Printf("%d HTTP ERROR:%s", paper.Pid, err)
    return
  }
  //按分辨率目录保存图片
  Dirname := DataRoot + strconv.Itoa(paper.Width) + "x" + strconv.Itoa(paper.Height) + "/"
  if ! isDirExist(Dirname) {
    os.Mkdir(Dirname, 0755);
    fmt.Printf("dir %s created\n", Dirname)
  }
  //根据URL文件名创建文件
  filename := filepath.Base(paper.Url)
  dst, err := os.Create(Dirname + filename)
  if err != nil {
    fmt.Println("%d HTTP ERROR:%s", paper.Pid, err)
    return
  }
  // 写入文件
  io.Copy(dst, res.Body)
}
func isDirExist(path string) bool {
  p, err := os.Stat(path)
  if err != nil {
    return os.IsExist(err)
  } else {
    return p.IsDir()
  }
}
func main() {
  //检查并创建临时目录
  if ! isDirExist(DataRoot) {
    os.Mkdir(DataRoot, 0755);
    fmt.Println("dir %s created", DataRoot)
  }
  //生成一个数据序列，用来获取分页
  pow := make([]int, 2)
  for i := range pow {
    if (i > 0) {
      url := strings.Replace(PageUrl, "{pid}", strconv.Itoa(i), -1);
      fmt.Println(i, url);
      response, err := http.Get(url)
      if( err != nil) {
        fmt.Println(err)
        continue
      }
      body, _ := ioutil.ReadAll(response.Body)
      js, err := simplejson.NewJson(body)
      //遍历data下的所有数据
      data := js.Get("data").MustArray()
      for _, v := range data {
        v := v.(map[string]interface{})
        for kk, vv := range v {
          if(kk == "file_id") {
            //这里 vv 是一个[]interface{} json.Number，不知道怎么取出值，这里用了比较傻的Sprintf
            vv := fmt.Sprintf("%s", vv)
            imgid,_ := strconv.Atoi(vv)
            url := fmt.Sprintf("http://s.qdcdn.com/c/%d,1920,1200.jpg", imgid)
            fmt.Println(kk, imgid, url);
            paper := &Wallpaper{imgid, url, 1920, 1200}
            SaveImage(paper);
          }
        }
      }
    }
  }
  fmt.Println("oh yes, all job done.")
}