不带导入功能的`go run * .go`文件如何访问功能？

Question

I'm following the Bookshelf tutorial on building web services on Google App Engine.

To start the app the tutorial runs go run app.go auth.go template.go. I don't understand how this works. For example, how is the parseTemplate method from template.go used in app.go without an import statement for template.go?

My understanding is that in a Go project we have an entry point file that has a main method. That file then imports packages to use them internally. What is the advantage of running these three files at once?

Answer 1

That example uses a single package, specifically the main package to implement everything.

Every package may consist of multiple files, even the main package. Inside the package you don't import anything, you can access everything from the package. Spec: Packages:

Go programs are constructed by linking together packages. A package in turn is constructed from one or more source files that together declare constants, types, variables and functions belonging to the package and which are accessible in all files of the same package. Those elements may be exported and used in another package.

When the special main package is broken into multiple files, that's when you have to list all when launching the app:

go run app.go auth.go template.go

If the example would be separated into multiple packages, only then would you have to import the other packges from main to access them.