title: always get "502 Bad gateway" when use app engine VM
body: <p>I'm trying to use the app engine VM for my project (env: Go). But am having problems I still haven't been able to resolve after days of searching:</p>
  
  <ol>
  <li><p>I can't use the package "google.golang.org/appengine" and "google.golang.org/cloud/*"
  When I deploy my code which contains the above packages I can deploy successfully, but when I access the URL, return always "502 Bad Gateway".
  If I deploy the code without the above package, all works very well</p></li>
  <li><p>The problem above happens after an update some of my package. Because I get this problem after I did "go get -u ...", before that all works well</p></li>
  <li><p>When I see the last commit here (package "google.golang.org/appengine"): <a href="https://github.com/golang/appengine/commit/25b8450bec636c6b6e3b9b33d3a3f55230b10812" rel="nofollow">https://github.com/golang/appengine/commit/25b8450bec636c6b6e3b9b33d3a3f55230b10812</a>
  I don't understand when replace "package helloworld" -> "package main". If I depoy with "package main", I don't know how to access the handler. For example:</p></li>
  </ol>
  
  <p><code>func main() {
      http.HandleFunc("/hello", helloHandler)
      appengine.Main()
  }</code></p>
  
  <p>After deploy, how to test?? Because "my_app.appspot.com/hello" return 404, page not found</p>
  
  <p>I don't know if there is someone else having the same problem. Please help, thanks!!!</p>