我已经尝试通过golang.com/x/oauth2库成功使用OAuth进行身份验证。

// provider variable is oauth2.Config
// scope is: https://www.googleapis.com/auth/userinfo.email
url := provider.AuthCodeURL(``) // redirect URL

从客户端重定向回后，我发送auth_code成功

auth_code := ctx.Request.URL.RawQuery // code=XXXX
if len(auth_code) > 5 {
    auth_code = auth_code[5:] // XXXX
}
tok, err := provider.Exchange(oauth2.NoContext, auth_code)
if err == nil {
    client := provider.Client(oauth2.NoContext, tok)
    email_url := `https://www.googleapis.com/auth/userinfo.email`
    //Log.Describe(client)
    response, err := client.Get(email_url) 
    if err == nil {
        ctx.Render(`login_oauth`, response)
        //handled = true
    }
}
//Log.Describe(err)

我发现什么都没有告诉电子邮件部分response（Body为空）：

{
    "Status": "200 OK",
    "StatusCode": 200,
    "Proto": "HTTP/1.1",
    "ProtoMajor": 1,
    "ProtoMinor": 1,
    "Header": {
        "Alternate-Protocol": [
            "443:quic,p=0.5"
        ],
        "Cache-Control": [
            "private, max-age=0"
        ],
        "Content-Type": [
            "text/plain"
        ],
        "Date": [
            "Tue, 14 Apr 2015 05:52:17 GMT"
        ],
        "Expires": [
            "Tue, 14 Apr 2015 05:52:17 GMT"
        ],
        "Server": [
            "GSE"
        ],
        "X-Content-Type-Options": [
            "nosniff"
        ],
        "X-Frame-Options": [
            "SAMEORIGIN"
        ],
        "X-Xss-Protection": [
            "1; mode=block"
        ]
    },
    "Body": {}, // empty!!!
    "ContentLength": -1,
    "TransferEncoding": [
        "chunked"
    ],
    "Close": false,
    "Trailer": null,
    "Request": {
        "Method": "GET",
        "URL": {
            "Scheme": "https",
            "Opaque": "",
            "User": null,
            "Host": "www.googleapis.com",
            "Path": "/auth/userinfo.email",
            "RawQuery": "",
            "Fragment": ""
        },
        "Proto": "HTTP/1.1",
        "ProtoMajor": 1,
        "ProtoMinor": 1,
        "Header": {
            "Authorization": [
                "Bearer ya29.VQFRHDe21t7g2cUhN8sUwjpRRi10XldgLe0RFhMe2ZxgyRo7q90HoKES5WmcucwKqtjZdq_KvYjKiQ"
            ]
        },
        "Body": null,
        "ContentLength": 0,
        "TransferEncoding": null,
        "Close": false,
        "Host": "www.googleapis.com",
        "Form": null,
        "PostForm": null,
        "MultipartForm": null,
        "Trailer": null,
        "RemoteAddr": "",
        "RequestURI": "",
        "TLS": null
    },
    "TLS": {
         // really long output
    }
}

第一个问题 ，如何正确获取电子邮件？无需使用Google+ API。

编辑＃2 我尝试将另一个scope用于oauth2.Config：

https://www.googleapis.com/auth/plus.profile.emails.read
https://www.googleapis.com/auth/plus.login
https://www.googleapis.com/auth/plus.me

并尝试使用较新的API检索电子邮件：

https://www.googleapis.com/plus/v1/people/me

但它给 403 Forbidden

编辑＃3 我尝试使用另一个范围：

openid
profile
email

并尝试使用以下URL检索电子邮件：

https://www.googleapis.com/oauth2/v3/userinfo

但它仍然Body像以前一样为空。

第二个问题 ，我可以为其他用户重用oauth2.Config（provider）变量吗？还是应该为每个用户创建一个副本？