The Within Go Repo Layout
Published on 09/07/2020, 1186 words, 5 minutes to read
Go repository layout is a very different thing compared to other languages. There's a lot of conflicting opinions and little firm guidance to help steer people along a path to more maintainable code. This is a collection of guidelines that help to facilitate understandable and idiomatic Go.
At a high level the following principles should be followed:
- If the code is designed to be consumed by other random people using that repository, it is made available for others to import
- If the code is NOT designed to be consumed by other random people using that repository, it is NOT made available for others to import
- Code should be as close to where it's used as possible
- Documentation helps understand why, not how
- More people can reuse your code than you think
At a minimum, the following folders should be present in the repository:
cmd/-> houses executable commands
docs/-> houses human readable documentation
internal/-> houses code not intended to be used by others
scripts/-> houses any scripts needed for meta-operations
Any additional code can be placed anywhere in the repo as long as it makes sense. More on this later in the document.
If there is code that should be available for other people outside of this project to use, it is better to make it a publicly available (not internal) package. If the code is also used across multiple parts of your program or is only intended for outside use, it should be in the repository root. If not, it should be as close to where it is used as makes sense. Consider this directory layout:
repo-root ├── cmd │ ├── paperwork │ │ ├── create │ │ │ └── create.go │ │ └── main.go │ ├── hospital │ │ ├── internal │ │ │ └── operate.go │ │ └── main.go │ └── integrator │ ├── integrate.go │ └── main.go ├── internal │ └── log_manipulate.go └── web ├── error.go └── instrument.go
This would expose packages
to be consumed by outside users. This would allow reuse of the error handling in
web, but it would not allow reuse of whatever manipulation is done to
logging in package
This folder has subfolders with go files in them. Each of these subfolders is
one command binary. The entrypoint of each command should be
main.go so that
it is easy to identify in a directory listing. This follows how the go standard
library does this.
repo-root └── cmd ├── paperwork │ └── main.go ├── hospital │ └── main.go └── integrator └── main.go
This would be for three commands named
As your commands get more complicated, it's tempting to create packages in
repo-root/internal/ to implement them. This is probably a bad idea. It's
better to create the packages in the same folder as the command, or optionally
internal package. Consider if
paperwork has a command named
hospital has a command named
integrator has a command named
repo-root └── cmd ├── paperwork │ ├── create │ │ └── create.go │ └── main.go ├── hospital │ ├── internal │ │ └── operate.go │ └── main.go └── integrator ├── integrate.go └── main.go
Each of these commands has the logic separated into different packages.
paperwork has the create command as a subpackage, meaning that other parts of the
application can consume that code if they need to.
hospital has the operate command inside its internal package, meaning only
cmd/foo/ and anything that has the same import path prefix can use that
This makes it easier to isolate the code so that other parts of the repo
cannot use it.
integrator has the integrate command as a separate go file in the main package of
the command. This makes the integrate command code only usable within the
command because main packages cannot be imported by other packages.
Each of these methods makes sense in some contexts and not in others. Real-world usage will probably see a mix of these depending on what makes sense.
This folder has human-readable documentation files. These files are intended to help humans understand how to use the program or reasons why the program was put together the way it was. This documentation should be in the language most common to the team of people developing the software.
The structure inside this folder is going to be very organic, so it is not entirely defined here.
The internal folder should house code that others shouldn't consume. This can be for many reasons. Generally if you cannot see a use for this code outside the context of the program you are developing, but it needs to be used across multiple packages in different areas of the repo, it should default to going here.
If the code is safe for public consumption, it should go elsewhere.
The scripts folder should contain each script that is needed for various operations. This could be for running fully automated tests in a docker container or packaging the program for distribution. These files should be documented as makes sense.
Code should be tested in the same folder that it's written in. See the upstream testing documentation for more information.
Integration tests or other things should be done in an internal subpackage called "integration" or similar.f
Questions and Answers
Why not use
pkg/ for packages you intend others to use?
pkg is already well-known in the Go ecosystem. It is the folder that
compiled packages (not command binaries) go. Using it creates the
potential for confusion between code that others are encouraged to use and the
meaning that the Go compiler toolchain has.
If a package prefix for publicly available code is really needed, choose a name not already known to the Go compiler toolchain such as "public".
How does this differ from https://github.com/golang-standards/project-layout?
This differs in a few key ways:
- Discourages the use of
pkg, because it's obvious if something is publicly available or not if it can be imported outside of the package
- Leaves the development team a lot more agency to decide how to name things
The core philosophy of this layout is that the developers should be able to decide how to put files into the repository.
But I really think I need
Set up another git repo for those libraries then. If they are so important that
other people need to use them, they should probably be in a
libraries repo or
individual git repos.
Besides, nothing is stopping you from actually using
pkg if you want to. Some
more experienced go programmers will protest though.
Examples of This in Action
Here are a few examples of views of this layout in action:
Facts and circumstances may have changed since publication. Please contact me before jumping to conclusions if something seems wrong or unclear.
Tags: go, standards