package main import (  "fmt"  "log"  "net/http"  "net/url"  "io/ioutil" ) //指定代理ip func getTransportFieldURL(proxy_addr *string) (transport *http.Transport) {  url_i := url.URL{}  url_proxy, _ := url_i.Parse(*proxy_addr)  transport = &http.Transport{Proxy : http.ProxyURL(url_proxy)}  return } //从环境变量$http_proxy或$HTTP_PROXY中获取HTTP代理地址 func getTransportFromEnvironment() (transport *http.Transport) {  transport = &http.Transport{Proxy : http.ProxyFromEnvironment}  return } func fetch(url , proxy_addr *string) (html string) {  transport := getTransportFieldURL(proxy_addr)  client := &http.Client{Transport : transport}  req, err := http.NewRequest("GET", *url, nil)  if err != nil {   log.Fatal(err.Error())  }  resp, err := client.Do(req)  if err != nil {   log.Fatal(err.Error())  }  if resp.StatusCode == 200 {   robots, err := ioutil.ReadAll(resp.Body);   resp.Body.Close()   if err != nil {    log.Fatal(err.Error())   }   html = string(robots);  } else {   html = ""  }  return } func main() {  proxy_addr := "http://183.221.250.137:80/"  url := "http://www.baidu.com/s?wd=ip"  html := fetch(&url, &proxy_addr)  fmt.Println(html) }