Added make release rule for automated building of the release binary

Makefile

@@ -1,5 +1,12 @@
 pkgs = $(shell go list ./...)
 
+BUILD_CONSTS = \
+	-X main.buildTime=`date -u '+%Y-%m-%d_%H:%M:%S'` \
+	-X main.buildRevision=`git rev-parse HEAD` \
+	-X main.buildTag=`git tag --points-at HEAD`
+
+BUILD_OPTS = -ldflags="$(BUILD_CONSTS)"
+
 install:
 	go get golang.org/x/crypto/acme/autocert
 	go get github.com/prometheus/client_golang/prometheus
@@ -9,7 +16,7 @@ format:
 	go fmt $(pkgs)
 
 build:
-	go build
+	go build $(BUILD_OPTS)
 
 test: build
 	go test -race -v $(pkgs)
@@ -18,4 +25,7 @@ run: build
 	./chproxy -config=testdata/http.conf.yml
 
 reconfigure:
-	kill -HUP `pidof chproxy`
+	kill -HUP `pidof chproxy`
+
+release:
+	GOOS=linux GOARCH=amd64 go build $(BUILD_OPTS) -o chproxy-linux-amd64

main.go

@@ -21,12 +21,10 @@ import (
 
 var (
 	configFile = flag.String("config", "", "Proxy configuration filename")
-	v          = flag.Bool("v", false, "Prints current version and exits")
+	version    = flag.Bool("version", false, "Prints current version and exits")
 )
 
 var (
-	version = "1.4.0"
-
 	proxy = newReverseProxy()
 
 	allowedNetworksHTTP    atomic.Value
@@ -36,12 +34,12 @@ var (
 
 func main() {
 	flag.Parse()
-	if *v {
-		fmt.Printf("Version %s\n", version)
+	if *version {
+		fmt.Printf("%s\n", versionString())
 		os.Exit(0)
 	}
 
-	log.Infof("Chproxy version: %s", version)
+	log.Infof("%s", versionString())
 	log.Infof("Loading config: %s", *configFile)
 	cfg, err := reloadConfig()
 	if err != nil {
@@ -216,3 +214,17 @@ func reloadConfig() (*config.Server, error) {
 	log.Infof("Loaded config: \n%s", cfg)
 	return &cfg.Server, nil
 }
+
+func versionString() string {
+	ver := buildTag
+	if len(ver) == 0 {
+		ver = "unknown"
+	}
+	return fmt.Sprintf("chproxy ver. %s, rev. %s, built at %s", ver, buildRevision, buildTime)
+}
+
+var (
+	buildTag      = "unknown"
+	buildRevision = "unknown"
+	buildTime     = "unknown"
+)