Embed version and revision

When is this valuable? When publishing software for traceability and referenc. I.e. for bug reports or documentation reference. Your applications can use flags such as -v or -version for this purpose. One way to modify variables during the build is via -ldflags.

Using -ldflags

First declare a variable, not constant, in the main package.

var (
	version  = "0.0"
	revision = "dev"
)

func main() {
	var showVersion bool
	flag.BoolVar(&showVersion, "v", false, "print version and exit")

	if showVersion {
		fmt.Printf("%s", version)
		os.Exit(0)
	}
}

Then compile and change the version with

go build -ldflags "-X main.version=0.1" ./cmd/app

You can also change multiple values in this way, let's add the revision as well

go build -ldflags "-X main.version=0.1 -X main.revision=alpha" ./cmd/app