Developing Go Modules In Private

Today brings us another reminder to read the reference materials, which will be your best source of information for any well-documented project. I’m primarily putting this out there as a reminder of that advice, and to point folks to the appropriate reference in this specific case.

I like that Go’s module system is an integrated part of the toolchain, and that for the most part it does The Right Thing. Until recently I thought that private modules were an exception to this. It turns out I was mercifully wrong.

Here’s the problem: I’m developing a small, personal project, and I want to break out a small subset of capability into a separate, library module. How do I import the new library from my larger project without making it public?

I was aware of private proxies, but that’s an entire server infrastructure that needs to be stood up, and this is a personal project. I didn’t want to take that on, but since that was a solution, I had assumed it was the solution. So my choice was between making the module public so I could import it via the standard channels, or standing up this server infrastructure.

That choice turned out to be a false one, because there’s a third, configuration-based option. And while I pride myself on preferring primary sources in software development (think API docs versus StackOverflow), I’ll admit I missed this option despite it being pretty clearly documented in the Go Modules Reference.

Okay, so here’s how to configure Go to grab private modules from a private repo. First, skip trying to download any module I’ve created via a proxy server by setting the GOPRIVATE environment variable to match my module prefix. Second, configure Git to re-write the URL Go would otherwise use to fetch my code by adding the following to my .gitconfig:

`[url "git@git.danielmoch.com:"]
    insteadOf = git://git.danielmoch.com/

If you’ve visited the Modules Reference already, but aren’t finding the relevant section, that’s because this whole solution is spread out over two sections. GOPRIVATE is discussed in Direct access to private modules, while the Git configuration was suggested in Passing credentials to private repositories.

So there you go. I hope you found this helpful, but more importantly I hope you’ve rediscovered the importance of reading the documentation.