net/http: add customization of proxy CONNECT requests

[AlmogBaku]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   1.6
2. What operating system and processor architecture are you using (go env)?
   darwin amd64 [os x]
3. What did you do?
   I tried to use Proxy with a Bearer authentication method.
4. What did you expect to see?
   Allow other authentication method than Basic HTTP
5. What did you see instead?
   Proxy authentication is limited to Basic-HTTP-Authentication only, with user & password:
   https://github.com/golang/go/blob/master/src/net/http/transport.go#L493
6. Suggestion
   • url.URL should allow custom authentication such as bearer
   • url.URL should provide a method that returns the "authentication header value", and do the base64 etc.

[bradfitz]

This proposal is a little confused. It's proposing modifications to url.URL, but talking about net/http stuff. I think you're probably looking for https://godoc.org/golang.org/x/oauth2 and friends. In general, I think everything you need is already on godoc.org somewhere.

Let's discuss your actual needs on the mailing list before jumping to proposals. See https://golang.org/wiki/Questions.

[mattn]

Well, I don't make sure but this seems not change of net/url. And maybe simply implementation of Transport.Proxy.

package main

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

func main() {
    token := "blur"
    http.DefaultClient.Transport.(*http.Transport).Proxy = func(r *http.Request) (*url.URL, error) {
        r.Header.Add("Authorization", "Bearer " + token)
        return r.URL, nil
    }
}

[AlmogBaku]

@mattn As I mentioned in the mailing-list, the problem is that when you do https, the CONNECT request wraps the original request, and there is no way to attach headers to the CONNECT req

[AlmogBaku]

@mattn see https://github.com/golang/go/blob/master/src/net/http/transport.go#L1031

[bradfitz]

This was added to Go 1.8. See https://beta.golang.org/pkg/net/http/#Transport.ProxyConnectHeader

Dup of #13290