Add a -version command-line switch to print the version

Fixes #2

dnscrypt-proxy/config.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -73,11 +74,16 @@ type BlockNameConfig struct {
 }
 
 func ConfigLoad(proxy *Proxy, svcFlag *string, config_file string) error {
+	version := flag.Bool("version", false, "prints current proxy version")
 	configFile := flag.String("config", "dnscrypt-proxy.toml", "path to the configuration file")
 	flag.Parse()
 	if *svcFlag == "stop" || *svcFlag == "uninstall" {
 		return nil
 	}
+	if *version {
+		fmt.Println(AppVersion)
+		os.Exit(0)
+	}
 	config := newConfig()
 	if _, err := toml.DecodeFile(*configFile, &config); err != nil {
 		return err

dnscrypt-proxy/main.go

@@ -15,6 +15,8 @@ import (
 	"golang.org/x/crypto/curve25519"
 )
 
+const AppVersion = "2.0.0beta2"
+
 type Proxy struct {
 	proxyPublicKey               [32]byte
 	proxySecretKey               [32]byte
@@ -153,7 +155,7 @@ func (proxy *Proxy) StartProxy() {
 	}
 	liveServers, err := proxy.serversInfo.refresh(proxy)
 	if liveServers > 0 {
-		dlog.Noticef("dnscrypt-proxy is ready - live servers: %d", liveServers)
+		dlog.Noticef("dnscrypt-proxy %s is ready - live servers: %d", AppVersion, liveServers)
 	} else if err != nil {
 		dlog.Error(err)
 		dlog.Notice("dnscrypt-proxy is waiting for at least one server to be reachable")