Set global variables on build time in Go

foo.go

package main

import "fmt"

// set these vars on build time:
// go build -ldflags "-X main.version=v1.2.3 -X main.commit=$(git rev-parse --short HEAD) -X main.date=$(date -u '+%Y-%m-%dT%H:%M:%S')" -o foo -v ./foo.go
var (
	service = "some-service"
	version string
	commit  string
	date    string
)

func main() {
	fmt.Printf("running %s on version %s, commit %s, build date %s\n",
		service, version, commit, date)
}