Go App Engine专案的套件结构

Question

I have been following Google App Engine's Go Tutorial.

According to the tutorial, I should create a root project directory and all source files related to the project should go into this directory. Consequentially, my workspace looks like this:

/MyProject
 /router
  router.go
 /items
  items.go

When I try to refer to items.go in router.go like this:

router.go

import(
    "items"
)

func itemsHandler(writer http.ResponseWriter, request * http.Request){
    anItem := items.Item{Id: 245,Name: "Chocolate",Price: 1.50};
}

The app fails to compile because items is undefined and now I am very confused about how a Go project on Google App Engine is supposed to be organised. What I'd like to know is

1. Is my project directory supposed to be located in the Go SDK's gopath directory or can it be located anywhere? The Tutorial did not make this clear.

2. What's the structure for a Go App Engine Project and how do I import the source files?

Answer 1

It seems theh cause of your problem is a missing src directory. .

1. Yes your project directory is supposed to be in the GOPATH. Go expects the directory structure to follow as described in the docs describing workspaces with all packages located in the src directory. When compiling it looks for packages in the gopath under the src folder (or pkg if installed). Although the App Engine docs do not specifically state this, it is my understanding that the structure should match the src structure.

2. An example of the directory structure is like this: starting with setting GOPATH=/myproject. In the directory of GOPATH, have the following structure (using some of your packages as an example).

   /src
    /MyApp/app.yaml
    /MyApp/myappmain.go
    /items/items.go
    /router/router.go
   

When I build I run the dev appserver by giving it the MyApp folder dev_appserver ./MyApp

I have tested this by putting log.Println("<pkg>") in every package init() func and they all only get run once as there was some people indicating this was a problem if you got the structure wrong.