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Go Tip: New releases, programatically
Jun 09, 2020

Last May I officially introduced versions, a tool for generating a report of dependencies from different Go-modules-like repositories, I mentioned some ideas I will be adding to versions really soon like different ways to render the final results (in a form of an image for example) and some extra attributes to add when parsing dependencies (like licenses used and packages with available new releases).

On that new releases topic I realized knowing a way to determine what are the most recent stable Go versions available is also a nice thing to have. The concrete use case for knowing the available Go versions is to determine when to upgrade to a new version or when to know the used version is no longer longer supported.

From a quick search I couldn’t find a way to know this right away, my initial thought was to get that information from the official downloads page in a form of a RSS feed or something similar, but this wasn’t available at the time.

Thankfully gophers-slack exists, I asked in #general and the community shared with me a few different ways to get this information:

Using golang.org/VERSION

Visiting https://golang.org/VERSION renders the most recent stable Go version in HTML, on that page there’s another link for getting a similar result in text format: https://golang.org/VERSION?m=text.

Using golang.org/dl

Everybody knows https://golang.org/dl/, the official Go downloads page, but did you know there’s another way to render those results? Using https://golang.org/dl/?mode=json. This endpoint renders a JSON response that, by default, gives us more details:

  • The two most recent and stable versions, and
  • Links to the all the different ways to download the compiler, categorized by platform and file type.

But not only that! The official documentation for golang.org/x/website/internal/dl also supports another query argument for returning more results: https://golang.org/dl/?mode=json&include=all, this returns a response including a full list of available downloads, including stable, unstable, and archived releases. Pretty neat.

Using github’s atom feed

I didn’t think about this option in the beginning but it definitely makes a lot of sense considering the Go project is also using Github. There’s a way to subscribe the to the Atom feeds for tags (https://github.com/golang/go/tags.atom) and releases (https://github.com/golang/go/releases.atom).

This option is a bit similar to the previous long form of https://golang.org/dl/?mode=json&include=all, it is useful for sure but it requires parsing the actual results in Atom format.

Conclusion

I bet there are more ways to get the available Go versions, like this one using gRPC, but I think the way to go here is to use the semi-official long form version (https://golang.org/dl/?mode=json&include=all) for this new feature, it includes more details and it is in JSON, so using a combination of net/http and encoding/json should suffice.


The more you know


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