go-linker-vars-example

This project is a simple example of using go build linker flags to set package variables deeper than just main which is well covered. I created this repo because I didn't find a good example on the topic of deeper variables which could be imported into multiple main packages. Full documentation for the go command.

NOTE: This repo example repo is built using Go 1.5.2, I know for a fact the flags changed since 1.4.x. However the same concepts should are available just check the documentation

Simple Configuration of main package variables

cd cmd/
go build -ldflags "-X main.MainVar=hihi"

$ ./cmd
MainVar: hihi
Version: 

Setting pathed package variables with linker flags

The github.com/ropes/go-linker-vars-example/src/version can then be imported into any Go package to access its exported variables.

cd cmd/
go build -ldflags "-X github.com/ropes/go-linker-vars-example/src/version.Version=hihi"
./cmd

Output:

MainVar: 
Version: hihi

Getting fancy with it!

Import the version package to where it will be exposed or logged:

package main

import "fmt"
import "github.com/ropes/go-linker-vars-example/src/version"

func main() {
	fmt.Printf("Git Tag:   %s\n", version.GitTag)
	fmt.Printf("Build User: %s\n", version.BuildUser)
	fmt.Printf("Version:   %s\n", version.Version)
}

Inject VCS and build information into the an importable package which can be referenced by multiple binaries via the go ``build or install commands.

cd cmd/complex
gittag=$(git describe --tags)

go build -ldflags "-X github.com/ropes/go-linker-vars-example/src/version.GitTag=${gittag} 
-X github.com/ropes/go-linker-vars-example/src/version.BuildUser=${USER} 
-X github.com/ropes/go-linker-vars-example/src/version.Version=v0.0.1"

Output:
$./complex 
Git Tag:    v0.0.1-1-gd75e8db
Build User: josh
Version:    v0.0.1