Google App Engine模块主机名：不是App Engine上下文

Question

I am trying to discover other deployed services on the App Engine. Something like this article suggests.

This is how my code looks like:

import (
    "fmt"
    "net/http"

    "google.golang.org/appengine"
)

func ServiceHostname(serviceName string, r *http.Request) (string, error) {
    ctx := appengine.NewContext(r)
    hostname, err := appengine.ModuleHostname(ctx, serviceName, "", "")
    if err != nil {
        return "", fmt.Errorf("unable to find service %s: %v", serviceName, err)
    }
    return hostname, nil
}

I am calling this function in a regular http handler. The error I've got is: not an App Engine context.

The only difference in between my code and the referenced article is in app engine go version. I am using the new go111 where he's using go1 runtime.

Do you know how to overcome the issue?

Answer 1

I found the solution. You need to call appengine.Main() in your main file even though it shouldn't be necessary to do in the new go111 runtime.

So the code in question stays the same, you need to register your handlers same as in go1.9 runtime.

func main() {
    http.HandleFunc("/serveurl", handle)
    appengine.Main()
}

Source: https://groups.google.com/d/msg/google-appengine-go/ZcASFMWJKpE/7iwGirNiBgAJ

It's alo mentioned in Writing a main package:

• Or, if your service is using the google.golang.org/appengine package, include a call to appengine.Main().