如何在Go中使用未共享的有状态变量？

Question

I know that, right now (and probably forever), we won't have static variables in Go... but is there a way to protect variables in some way?

import (
    "net/http"
    "net/http/cookiejar"
)

func funcThatDoesRequests(request Request) (response Response, e error){
  static cookieJar, _ := cookiejar.New(nil)
  static client := http.Client{ Jar: cookieJar }
  response, e = client.Do(handshakeRequest)
  return
}

I don't want the http client and its cookieJar floating around so other functions can do something with them. I need the cookieJar and client to only be accessible inside the funcThatDoesRequests. Is that possible?

Static variables (see static keyword in the pseudo code example) is a feature present in languages like C and PHP, to name some common languages.

Answer 1

Usually it's best not to worry about package-scoped globals since it's only code in your own package that can abuse them.

But if you really want, you can use a closure which is created when your package is loaded to generate the "static" variables.

func makeFunc() func(req Request)(Response, error) {
    cookieJar, _ := cookiejar.New(nil)
    client := http.Client{Jar: cookieJar}
    return func(req Request)(Response, error) {
        return client.Do(handshakeRequest)
    }
}

var funcThatDoesRequests = makeFunc()

Now funcThatDoesRequests maintains client and cookieJar over multiple calls, but the names don't leak into the package.