go程序抛出错误找不到程序包“；code.google.com/p/go.net/websocket“；

我是编程语言新手。下面是我的代码

package main

import (
    "code.google.com/p/go.net/websocket"
    "fmt"
    "net/http"
    "strconv"
)

var add := "12345"

func EchoLengthServer(ws *webscoket.Conn) {
    var msg string

    for {
        websocket.Message.Receive(ws, &msg)
        fmt.Println("Got Message", msg)
        length := len(msg)
        if err := websocket.Message.Send(ws, strconv.FormatInt(int64(length), 10)); err != nil {
            fmt.Println("can't send message length")
            break
        }
    }
}

func websocketListen() {
    http.Handle("/length", websocket.Handler(EchoLengthServer))
    err := http.ListenAndServe(addr, nil)
    if err != nil {
        panic("ListenAndServe:" + err.Error())
    }
}

当我执行代码时，我发现了下面的错误

[rajkumar@localhost ch4-DesigningAPI]$ go run WebSockets.go 
WebSockets.go:6:3: cannot find package "code.google.com/p/go.net/websocket" in any of:
    /usr/local/go/src/code.google.com/p/go.net/websocket (from $GOROOT)
    /home/rajkumar/GOPackages/src/code.google.com/p/go.net/websocket (from $GOPATH)

我试图通过go get命令在GOPATH中添加websocket包，但这也引发了下面的错误

[rajkumar@localhost ch4-DesigningAPI]$ go get code.google.com/p/go.net/websocket
go: missing Mercurial command. See http://golang.org/s/gogetcmd
package code.google.com/p/go.net/websocket: exec: "hg": executable file not found in $PATH

你能帮我解决这个错误吗。

这个怎么样

$ go get -v golang.org/x/net/websocket
golang.org/x/net/websocket
$

-

---

只需安装Mercurial。这与围棋无关。@Volker:is

code.google.com/p/go.net/websocket

已过时：。@Peter是的，但导入旧版本（无论出于何种原因）需要Mercurial。顺便说一句：我对你的答案投了赞成票。谢谢沃克和彼得。这个命令正在神奇地工作。谢谢你的帮助。下面是主要功能

package main

import (
    "fmt"
    "net/http"
    "strconv"

    "golang.org/x/net/websocket"
)

var addr = "12345"

func EchoLengthServer(ws *websocket.Conn) {
    var msg string

    for {
        websocket.Message.Receive(ws, &msg)
        fmt.Println("Got Message", msg)
        length := len(msg)
        if err := websocket.Message.Send(ws, strconv.FormatInt(int64(length), 10)); err != nil {
            fmt.Println("can't send message length")
            break
        }
    }
}

func websocketListen() {
    http.Handle("/length", websocket.Handler(EchoLengthServer))
    err := http.ListenAndServe(addr, nil)
    if err != nil {
        panic("ListenAndServe:" + err.Error())
    }
}

func main() {}