如何从Google App Engine Standard Env for Go中的request.RemoteAddr和X-AppEngine-Country，Region等获取输出？

问题描述：

I have a service running in the Google App Engine Standard Environment written in Go that is configured to use the latest runtime at deployment (api_version: go1 - which is currently Go 1.8).

In this service I inspect the request headers for various purposes.

func extractHeaders(res http.ResponseWriter, req *http.Request) {
    ctx := appengine.NewContext(req)
    clientIPAddress, _, _ := net.SplitHostPort(req.RemoteAddr) // Output is blank
    country := req.Header.Get("X-AppEngine-Country") // Output: US
    region := req.Header.Get("X-AppEngine-Region") // Output: ?
    city := req.Header.Get("X-AppEngine-City") // Output: ?
    cityLatLong := req.Header.Get("X-AppEngine-CityLatLong") // Output 0.000000,0.000000
    ...
}

As seen in the inline comment for the lines beginning where I read the RemoteAddr field, I am not getting the output I expected per the AppEngine Standard documentation found here (How Requests are Handled | App Engine standard environment for Go | Google Cloud Platform).

While the documentation states the that X-AppEngine-* may not always be able to be filled in based on the IP address of the client request, I am never seeing them filled in with data other than that which I listed.

Is there any configuration required to get these headers (and the RemoteAddr field) populated in the App Engine Standard Environment for Go? Am I simply misunderstanding the documentation?

我在用Go语言编写的Google App Engine标准环境中运行了一项服务，该服务配置为使用以下最新运行时部署（api_version：go1-当前为Go 1.8）。 p>

在此服务中，出于各种目的，我检查请求标头。 p>

  func extractHeaders（res http.ResponseWriter，req * http.Request）{
 ctx：= appengine.NewContext（req）
 clientIPAddress，_，_：= net  .SplitHostPort（req.RemoteAddr）//输出为空白
国家：= req.Header.Get（“ X-AppEngine-Country”）//输出：美国
地区：= req.Header.Get（“ X-  AppEngine-Region“）//输出：？
 city：= req.Header.Get（” X-AppEngine-City“）//输出：？
 cityLatLong：= req.Header.Get（” X-AppEngine-  CityLatLong“）//输出0.000000,0.000000 
 ... 
} 
  code>  pre> 
 
 如在我读RemoteAddr字段开始的行的内联注释中所见 ，我没有获得按照此处（如何处理请求| Go的App Engine标准环境| Google Cloud Platform）。 p> 
 
 
文档中指出X-AppEngine- *可能无法 总是能够 要根据客户端请求的IP地址进行填充，我从来没有看到它们填充了我列出的数据以外的数据。 p> 
 
 
是否需要进行任何配置才能获取这些标头 （和RemoteAddr字段）填充到Go的App Engine标准环境中？ 我只是误解了文档吗？ p> 
  div>

答

One thing to note is that req.RemoteAddr is going to end up with the IP address of the last proxy in the chain to your app. On App Engine that's probably going to end up being 127.0.0.1. net.SplitHostPort is likely erroring since the IP may not actually have a Port number.

The Region, City, and CityLatLong data are going to come from your IP, if that information is available, it may not be as it's not strictly required. What you can try is to pull the IP address from the X-Forwarded-For header. This will typically give you the full list of proxies and the originating IP address (IPv4 or IPv6, see example results below).

If you were to use: package hello

import (
    "fmt"
    "net"
    "net/http"
)

func init() {
    http.HandleFunc("/", handler)
}

func handler(w http.ResponseWriter, r *http.Request) {
    clientIPAddress, _, err := net.SplitHostPort(r.RemoteAddr)
    if err != nil {
        clientIPAddress = err.Error()
    }
    rAddr := r.RemoteAddr
    forward := r.Header.Get("x-forwarded-for")
    country := r.Header.Get("X-AppEngineCountry")
    region := r.Header.Get("X-AppEngine-Region")
    city := r.Header.Get("X-AppEngine-City")
    cityLatLong := r.Header.Get("X-AppEngine-CityLatLong")
    fullHeader := r.Header
    fmt.Fprintf(w, "Hello, world!
 %v
 %v
 %v
 %v
 %v
 %v
 %v
 %v",
        clientIPAddress,
        rAddr,
        forward,
        country,
        region,
        city,
        cityLatLong,
        fullHeader
    )
}

You should see something similar to (as long as Region City, CityLatLong are avaliable otherwise those will be blank):

Hello, world!
 missing port in address 127.0.0.1
 127.0.0.1
 2601:1c2:600:17b0::::, 2607:f8b0:400a:::2014
 ZZ
 or
 portland
 45.523452,-122.676207
 map[Accept-Encoding:[identity] X-Appengine-Default-Version-Hostname:
[127.0.0.1:8080] X-Appengine-User-Organization:[] X-Appengine-Citylatlong:
[45.523452,-122.676207] X-Appengine-Request-Log-Id:
[48f03baada92bbb3872a8b3a5baa3f8b0dfff413f64fbcfa] X-
Appengine-City:[portland] X-Forwarded-Proto:[https] X-Appengine-Server-Name:
[127.0.0.1] Via:[1.1 google] X-Appengine-Server-Software:[Development/2.0] 
X-Appengine-User-Id:[] X-Forwarded-For:
[2601:1c2:600:17b0:::: 2607:f8b0:400a:::2014] X-Goog-
Cloud-Shell-Target-Host:[127.0.0.1] X-Appengine-Country:[ZZ] Accept:
etc
etc

Hope that helps.

如何从Google App Engine Standard Env for Go中的request.RemoteAddr和X-AppEngine-Country，Region等获取输出？

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