Version in Golang
I am writing more Go services enough to just forgot the current version in production/staging. With nodejs, it is as simple as exporting from package.json.
Go does not have a thing like package.json, and I would expect the version should return more than just the version: build time, git hash, and git tag. That information will be inserted into the binary during the build.
At first, the needed information from the shell:
- timestamp: `date -u '+%Y-%m-%d_%I:%M:%S%p'`. (e.g. 2018-10-13_08:26:34AM)
- githash: `git rev-parse HEAD`
- gittag: `git describe --tags $(git rev-list --tags --max-count=1)`
How to pass the value to the artifact? From one issue in Go https://github.com/golang/go/issues/18246, yay Go should need a better doc for this, the method is
-ldflags "-X importpath.name=value".
Then the makefile:
buildtime=`date -u '+%Y-%m-%d_%I:%M:%S%p'`
githash=`git rev-parse HEAD`
gittag=`git describe --tags $(git rev-list --tags --max-count=1)`
LDFLAGS="-X gitlab.com/nqd/example/handlers.buildstamp=$buildtime -X gitlab.com/nqd/example/handlers.githash=$githash -X gitlab.com/nqd/example/handlers.gittag=$gittag"
The makefile tells Go compiler to replace buildstamp, githash, and gittag from value pass by the shell variables. Build the artifact with this LDFLAGS: $(GO) build -ldflags $(LDFLAGS) ...
At handlers.go where the buildstamp, githash, and gittag can be exported via one API:
var buildstamp = "no buildstamp provided"
var githash = "no githash provided"
var gittag = "no tag"
type statuser struct {
Build string `json:"build"`
Time string `json:"time"`
Version string `json:"version"`
}
func (s *statuser) Render(w http.ResponseWriter, r *http.Request) error {
render.Status(r, 200)
return nil
}
func status(w http.ResponseWriter, r *http.Request) {
st := statuser{
Build: githash,
Time: buildstamp,
Version: gittag,
}
render.Render(w, r, &st)
}
For the same method, we can inject any information into binary artifact during compiling.