version

Simply get the version information from Go BuildInfo.

Usage:

import "github.com/imjasonh/version"

func main() {
    fmt.Println(version.Get())
}

This code is not maintained, and I will not accept PRs. Fork it if you want it. It's like 50 lines, just copy it into your codebase.

Please stop using ldflags to embed this information. Or if you do, at least embed a reproducible time.

---

Rant

Since the early days of Go, if you wanted to embed something like the Git commit that was built in your binary, you had to do something janky like

package main

const commit = "unknown"

and

go build -ldflags="-X 'main.commit=$(git rev-parse HEAD)'"

This was kinda gross, but it worked, so people did it. And boy did they do it. This little trick got cargo-culted all over the place! Anecdotally, basically any Go application you use has its version embedded this way.

Sometimes folks also wanted a build date embedded, and okay, sure, we can do that too:

go build -ldflags="-X 'main.buildDate=$(date +%Y-%m-%dT%H:%M:%SZ)'"

Boom, done. Except...

That's going to cause your build to be non-reproducible. If you build that right now, wait ten seconds, and build it again, you'll get a new binary. You probably don't care that they were built 10 seconds apart from the same source. What you wanted was

go build -ldflags="-X 'main.buildDate=$(date -d@$SOURCE_DATE_EPOCH +%Y-%m-%dT%H:%M:%SZ)'"

and some sane static value of SOURCE_DATE_EPOCH to make that reproducible. Most folks would opt for the date of the commit that it's built from as a sane approach.

But you don't need to do any of this at all, so stop!

Since Go 1.12, back in 2019, the Go compiler has embedded this exact information for you, without you needing to know what an ldflag is. You can just call debug.ReadBuildInfo and it'll pop right out, along with a bunch of other stuff.

The vcs.revision and vcs.time are exactly the same as git rev-parse HEAD and "the date of that commit". So stop mucking with ldflags, and especially stop embedding a non-reproducible time. You're working too hard.

This package demonstrates this, and encapsulates it in version.Get. If you want to change anything about the behavior, copy the code and go for it. I wrapped it in a sync.OnceFunc so it didn't have to read the info each time, in case you call it multiple times. You're welcome.