dep is a dependency management tool for golang. If you have work on other programming languages, dep is similar to npm, pod or pip. In simple words, it is a package manager to manage your project's third party libraries.

How to install it

There's a few ways to install dep. Personally, I prefer to install it with Homebrew To install it run:

$~ brew install dep

Initializing a project with dep

To initialize it in your go project, go to your project directory and run the following

$~ dep init

This will create three things in your directory

1. Gopkg.toml: This where you specifies the project dependencies
2. Gopkg.lock: File generated as a result from running dep. It's a complete dependency graph for your project. You shouldn't edit this manually.
3. vendor/: This is where the dependencies are stored

dep init will behave differently depending on the state of your project.

If it is a new project, Gopkg.toml and vendor/ will be essentially empty aside from the usual commented out guides on how to use it.

If it is an existing project, Gopkg.toml adn vendor/ will add all the dependencies that you have added in your project with go get.

How to use dep?

Adding a new depencies

To add a new depencies in your project, run the following

$~ dep ensure -add <DEPENDENCIES>

Replace <DEPENDENCIES> with the path to its project repo. For example

$~ dep ensure -add github.com/gorilla/mux

Others

A few more commands that I find useful:

1. dep status: Will report the status of your project dependencies
2. dep prune: Will tell you which libraries that are out of sync

Conclusion

I am sure by now you are asking "why should I use go dep when go already comes with go get?".

Well, imagine you are working in a team project that uses a lot of dependencies. Each having their own version of libraries. Pretty soon you will have those "Works on my machine!" real quick.

dep solve this by making sure everyone who works on the project is guaranteed to be using the same version of dependencies.

That's it. Hopefully now you have learned the basic usage sof go dep to manage your project dependencies.