How to have unshared stateful variables in Go? - static

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.

Answer 2

One possibility would be to create a struct with your "private, static" variables and make your handler a method of that struct.
type privateData struct {
jar *cookiejar.Jar
client http.Client
}
func (r *privateData) Initialize() {
r.jar = cookiejar.New(nil)
r.client = http.Client{Jar: r.jar}
}
func (r *privateData) Do (request Request) (response Response, e error) {
/* Rest of the code goes here */
}
/* then, somewhere... */
var thing privateData
thing.Initialize()
/* then you can pass thing.Do where you would have passed funcThatDoesRequests */