Original post

Development for Modules continues in Go 1.13 and the support has for them too. Today, we’ll have a look at how to transform our development model to use them without hassle.

This series of articles is broken down into the following sections:

  • Starting with a new Go Module from scratch
  • Dependencies and how to use them*
    • Changing the version of a dependency
    • Using the vendoring mode
    • Tidying up the modules in a project
    • Visualising the dependencies of a project
  • Versioning and migrating to a new major version*
    • Non-major version upgrading
    • Major version upgrading
    • Using a dependency with a new major version

*Coming in future posts.

Let’s start by making sure that we are working with the latest version of Go. While Go 1.11 is the minimum Go version that uses , the recent developments in Go 1.13 mean that is it better for this type of project.

The same is true for GoLand. Make sure that you have GoLand 2019.3.2 or newer installed, as this series relies on the found in this newer version of the IDE.

Once you have everything in place, start the IDE and click on the New Project option. Then, select Go Modules (vgo) and choose where to place the project. You can select any folder on the computer, as we are no longer limited to GOPATH. Then, make sure to use the latest Go SDK as mentioned above, and select whether you want to use the vendoring mode or not.

You’ll also see that there’s an option to configure the proxy. By default, GoLand uses “direct” as a value. This means that Go will connect directly to the dependency location, e.g. Github, to fetch it. However, you can also point it to your own proxy server if you work in a company that doesn’t allow direct internet connections or wants a clear record of what dependencies and versions are used. Go uses “https://proxy..org,direct” as the default value, but this is overwritten by the value in the IDE proxy field.

Using Go Modules - 01 - creating a project

After the project is created, the project will contain a new file called go.mod. This file is the equivalent to the package.json from Node.js or requirements.txt from Python’s pip command. It contains the name of the module, the minimum Go version the module is compatible with, and any required third-party packages.

By default, the IDE automatically sets the module name to be the name of the folder, but we can customize it to whatever we want. In this case, I’ll change it to point to the Github hosted repository, e.g., github.com/dlsniper/modulesdemo.

If we want to make this module backward compatible with previous versions of Go without using any new features, we can also change the “go” version from “go 1.13” to another version, such as “go 1.11” or “go 1.12”.

Using Go Modules - 02 - changing the minimum go version

Now let’s create a new file and add some sample code. We’ll use the example below to make sure that we also get some dependencies in place.

After pasting this code into the editor, the import line for “github.com/gorilla/mux” becomes red. This happens because the import is not yet included in the go.mod file, so the IDE does not have enough information about the version of the package that we are using or where to get it from the cache.

Using Go Modules - 03 - using code with dependencies

To download the missing dependency, move the cursor over using the F2 shortcut (Next Highlighted Error) and then press Alt+Enter to invoke the Sync packages of …. This will automatically download and install any of the missing dependencies and their related packages.

We’ll talk about how to manage dependencies later.

Using Go Modules - 04 - adding missing dependencies to the project

When the operation finishes, everything will be green again and we can run the project as usual. To test this, let’s press Ctrl+Shift+F10 on Windows or Linux, or Cmd+Shift+R on macOS, to compile and run the application.

Using Go Modules - 05 - running go modules application

To test the debugging functionality, place a breakpoint on line 12, and run the debugger by pressing Alt+Shift+F9 on Windows/Linux, or Cmd+Option+D on macOS.

Using Go Modules - 06 - debugging go modules

Given that Go modules simply offer another way to represent the dependencies of our code, the running or debugging part of our workflow remains unchanged.

This concludes the first part of our series. We’ve seen how to create a new project, add a dependency to it, and then run or debug it.

In the next article, we’ll look at how to manage our dependencies.

Thank you for reading. If you have any suggestions, questions, or would like to provide us with feedback, please use the comments section below, our issue tracker, or our Twitter account.