Add CLI option to show version

main.go

@@ -5,6 +5,7 @@ package main
 import (
 	"encoding/json"
 	"flag"
+	"fmt"
 	"log"
 	"net"
 	"net/http"
@@ -18,16 +19,27 @@ const defaultPort = 6065
 // verbose tracks whether the program is operating in verbose mode
 var verbose bool
 
+// This is set to the actual version by GoReleaser as it's run. Versions built
+// from source will always show master.
+var version = "master"
+
 // ---
 
 func main() {
+	var showVersion bool
 	var port int
 	var unix string
 	flag.IntVar(&port, "port", 0, "Port to listen on")
 	flag.StringVar(&unix, "unix", "", "Unix socket to listen on")
 	flag.BoolVar(&verbose, "verbose", false, "Enable verbose mode")
+	flag.BoolVar(&showVersion, "version", false, "Show version")
 	flag.Parse()
 
+	if showVersion || len(flag.Args()) == 1 && flag.Arg(0) == "version" {
+		fmt.Printf("%s\n", version)
+		return
+	}
+
 	if unix != "" && port != 0 {
 		flag.Usage()
 		log.Fatalf("Specify only one of -port or -unix")