将一个主程序包放在cmd / myapp子目录中可以吗？

Question

this is my first Go project and I have had a hard time grasping the different documents on code organization (e.g. I found it somewhat hard to tell which ones have been superceded, or apply to deprecated vendoring tools/approaches). I finally settled on Ben Johnson's Standard Package Layout, with a very slim root package (in the root directory of my project) and most code in internal/pkg/...

However, I've added a cmd/myapp dir and put my main.go file for the executable program in there, since I understood that to be a common pattern.

So now I have:

myapp
|
+- myapp.go   // "package myapp", with only type and interface declarations and no imports
|
+- cmd
|   |
|   +- main.go // "package main", with import gitlab.tld/username/myapp, gitlab.tld/username/myapp/internal/pkg/routing etc.
|
+- internal
    |
    +- pkg
        |
        +- routing
        |    |
        |    +- routing.go // "package routing"
        |
        +- sql 
        |
        +- etc.

Now, when I go to cmd/myapp and call go build, it builds fine and leaves an executable that does what it's supposed to do right there. But when I call go build -v from the project's main directory, no executable is produced. In fact, only myapp.go seems to be processed which contains only type definitions. (And of course, go install does not produce a binary either. go get -v gitlab.tld/username/myapp also does not seem to do anything.)

So I have the suspicion that this is not how it is meant after all, but I am not even so sure about that. Is there a problem with the project layout, or did I get the usage of go tooling wrong?

Thanks for any help you might provide to this go newbie,

Andreas

Answer 1

When you run go build or go install the command expects a list of packages to process. If no import paths are given, the action applies to the package in the current directory.

So if there is no package main in your root directory, no executable will be produced.

The command doesn't look in subdirectories. You may have multiple commands in your cmd directory. In this case it won't know which one to build. And building all of them every time is wasteful.