Golang错误：未定义：http.NewSingleHostReverseProxy

Question

I tried building a simple program using Golang, here it is:

package main

import (
        "net/http"
        "net/http/httputil"
        "log"
)

func main(){

        proxy := http.NewSingleHostReverseProxy( &http.URL{Scheme:"http",Host:"www.google.com",Path:"/"})

        err := http.ListenAndServe(":8080", proxy)
        if err != nil {
                log.Fatal("ListenAndServe: ", err.String())
        }
}

Build:

go build myprogram.go

Output:

command-line-arguments
./myprogram.go:5: imported and not used: "net/http/httputil"
./myprogram.go:11: undefined: http.NewSingleHostReverseProxy
./myprogram.go:11: undefined: http.URL
./myprogram.go:15: err.String undefined (type error has no field or method String)

I noticed that http.NewSingleHostReverseProxy is in the "net/http/httputil" package, so why did I see such errors? Maybe I need a specific command to build it correctly?

EDIT Afterwords, here is the new working code:

package main

import (
        "net/http"
        "net/http/httputil"
        "net/url"
        "log"
)

func main(){

        proxy := httputil.NewSingleHostReverseProxy( &url.URL{Scheme:"http",Host:"www.google.com",Path:"/"})

        err := http.ListenAndServe(":8080", proxy)
        if err != nil {
                log.Fatal("ListenAndServe: ", err)
        }
}

Answer 1

I added

"net/url"

And replaced http.NewSingleHostReverseProxy with httputil.NewSingleHostReverseProxy, also http.URL with url.URL.

This is the working code:

package main

import (
"net/http"
"net/http/httputil"
"net/url"
"log"
)

func main(){

proxy := httputil.NewSingleHostReverseProxy( &url.URL{Scheme:"http",Host:"www.google.com",Path:"/"})

err := http.ListenAndServe(":8080", proxy)
if err != nil {
        log.Fatal("ListenAndServe: ", err)
}
}

Thanks to raina77ow for help.