One directory that we haven't mentioned so far is the vendor directory. The vendor directory in a Go project is a special directory. This is where dependency management for your project will be stored. For our book's long sample project, we will be using the dep tool. Concisely, dep is a dependency management tool that will allow you to version pin your dependencies to a project. It works by taking all of the imported packages that were retrieved with go get or git commands directly in your $GOPATH and copies the relevant source code needed by your project into this vendor directory within your project. The tool does this by reading your source code import statements and figuring out which packages you need. To get us started, we need to get the dep command with the following command:

go get -u github.com/golang/dep/cmd/dep

After we install the dep tool, we can initialize our project's vendor directory, as shown in the following code. When the dep tool initializes a project, it will take all of the dependencies you have imported and put the code in the vendor directory:

dep init

It is highly recommended that some form of dependency management is used within Go projects. There is nothing worse than a project build failure related to the removal of a dependency from the internet, such as the left-pad issue with NPM. You can avoid this type of issue by committing the vendor directory directly into your repository, and versioning it with the rest of your code. There are drawbacks to this approach—namely, that the size of pull and merge requests grow very large when there are significant changes to the dependencies of a project. It is the author's opinion, however, that these sorts of large dependency changes are indicative of possibly a larger workflow problem.

With this strong structural foundation in place, we are ready to begin the process of creating our application. The remainder of this chapter will briefly touch on the major features within the Echo framework.