Print binary version info on gateway startup (observatorium#649)

Signed-off-by: Ruben Vargas <[email protected]>

Author: rubenvp8510

Diff for: Makefile

@@ -8,6 +8,8 @@ OS ?= $(shell go env GOOS)
 ARCH ?= $(shell go env GOARCH)
 BIN_NAME ?= observatorium-api
 FILES_TO_FMT ?= $(filter-out ./ratelimit/gubernator/gubernator.pb.go, $(shell find . -path ./vendor -not -prune -o -name '*.go' -print))
+GIT_BRANCH := $(shell git rev-parse --abbrev-ref HEAD)
+GIT_REVISION := $(shell git rev-parse --short HEAD)
 
 VERSION := $(strip $(shell [ -d .git ] && git describe --always --tags --dirty))
 BUILD_DATE := $(shell date -u +"%Y-%m-%d")
@@ -79,7 +81,7 @@ benchmark.md: $(EMBEDMD) tmp/load_help.txt
 	$(EMBEDMD) -w docs/benchmark.md
 
 $(BIN_NAME): deps main.go rules/rules.go $(wildcard *.go) $(wildcard */*.go)
-	CGO_ENABLED=0 GOOS=$(OS) GOARCH=$(ARCH) GO111MODULE=on GOPROXY=https://proxy.golang.org go build -a -ldflags '-s -w' -o $(BIN_NAME) .
+	CGO_ENABLED=0 GOOS=$(OS) GOARCH=$(ARCH) GO111MODULE=on GOPROXY=https://proxy.golang.org go build -a -ldflags '-s -w  -X main.Version=$(VERSION) -X main.Branch=$(GIT_BRANCH) -X main.Revision=$(GIT_REVISION)' -o $(BIN_NAME) .
 
 %.y.go: %.y | $(GOYACC)
 	$(GOYACC) -p $(basename $(notdir $<)) -o $@ $<

Diff for: main.go

@@ -82,6 +82,13 @@ const (
 	gracePeriod = 2 * time.Minute
 )
 
+// Version is set via build flag -ldflags -X main.Version.
+var (
+	Version  string
+	Branch   string
+	Revision string
+)
+
 type config struct {
 	logLevel  string
 	logFormat string
@@ -258,13 +265,21 @@ type tenant struct {
 	} `json:"rateLimits"`
 }
 
+func init() {
+	version.Version = Version
+	version.Branch = Branch
+	version.Revision = Revision
+}
+
 //nolint:funlen,gocyclo,gocognit
 func main() {
 	cfg, err := parseFlags()
 	if err != nil {
 		stdlog.Fatalf("parse flag: %v", err)
 	}
 
+	stdlog.Println(version.Info())
+
 	if !cfg.metrics.enabled && !cfg.logs.enabled && !cfg.traces.enabled {
 		stdlog.Fatal("Neither logging, metrics not traces endpoints are enabled. " +
 			"Specifying at least a logging or a metrics endpoint is mandatory")
@@ -1018,7 +1033,6 @@ func parseFlags() (config, error) {
 	)
 
 	cfg := config{}
-
 	flag.StringVar(&cfg.rbacConfigPath, "rbac.config", "rbac.yaml",
 		"Path to the RBAC configuration file.")
 	flag.StringVar(&cfg.tenantsConfigPath, "tenants.config", "tenants.yaml",