在Go中调试两足式OAuth2

Question

I am working on implementing a client library for a remote API which uses 2-legged OAuth2 for authentication.

package main

import (
    "net/http"
    "golang.org/x/oauth2/clientcredentials"
    "golang.org/x/net/context"
)

type SpecialClient struct {
    *http.Client
}

func NewClient(cid, cis string) *SpecialClient {
    tconf := clientcredentials.Config{
        ClientID:     cid,
        ClientSecret: cis,
        TokenURL:     "http://some.remote.resource/token",
    }

    c := tconf.Client(context.Background())
    return &SpecialClient{c}
}

func main() {
    c := NewClient("clientID", "clientSecret")
    c.Get("http://some.remote.resource/path/to/resource")
}

It is extremely straightforward. Right now, I think the remote API's OAuth2 implementation is broken, as it's not returning a token properly according to RFC 6749. I'm trying to debug the client creation with golang.org/x/oauth2/clientcredentials, but I cannot determine at which point a token is fetched from the token URL. I've stepped through almost 100 calls with delve, and I do not see the client creating a new request to fetch a token. Is there a way I can review the request created by the *http.Client used to retrieve the token?