add version flag

cli.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 
 	"github.com/jessevdk/go-flags"
@@ -12,12 +13,19 @@ type GlobalOptions struct {
 	TLSKey    string `long:"tlskey" value-name:"~/.docker/key.pem" description:"Path to TLS key file"`
 	TLSVerify bool   `long:"tlsverify" description:"Use TLS and verify the remote"`
 	Host      string `long:"host" short:"H" value-name:"unix:///var/run/docker.sock" description:"Docker host to connect to"`
+	Version   func() `long:"version" short:"v" description:"Display version information."`
 }
 
 var globalOptions GlobalOptions
 var parser = flags.NewParser(&globalOptions, flags.Default)
 
+var version = "v0.2"
+
 func main() {
+	globalOptions.Version = func() {
+		fmt.Println("dockviz", version)
+		os.Exit(0)
+	}
 	if _, err := parser.Parse(); err != nil {
 		os.Exit(1)
 	}