Print the server version with command line (Shopify#353)

Add flag `-version` to print the current version and exit.

```shell
$ toxiproxy-server -version
toxiproxy-server version v2.3.0
```

Author: miry

bin/e2e

@@ -22,7 +22,7 @@ go run testing/endpoint.go 2>&1 | sed -e 's/^/[web] /' &
 
 echo "=== Starting Toxiproxy"
 
-LOG_LEVEL=debug ./dist/toxiproxy-server  2>&1 | sed -e 's/^/[toxiproxy] /' &
+LOG_LEVEL=debug ./dist/toxiproxy-server 2>&1 | sed -e 's/^/[toxiproxy] /' &
 
 echo "=== Wait when service are available"
 

bin/release_test

@@ -9,15 +9,18 @@ if [ $ARCH == "x86_64" ]; then
   ARCH="amd64"
 fi
 
-docker run -v $(PWD)/dist:/dist --pull always --rm -it ubuntu bash -c "set -xe; dpkg -i /dist/toxiproxy_*_linux_${ARCH}.deb; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-cli --version ; /usr/bin/toxiproxy-cli --version | grep -o -e 'toxiproxy-cli version ${VERSION}'"
-docker run -v $(PWD)/dist:/dist --pull always --rm -it centos bash -c "set -xe; yum install -y /dist/toxiproxy_*_linux_${ARCH}.rpm; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-cli --version | grep \"toxiproxy-cli version ${VERSION}\""
-docker run -v $(PWD)/dist:/dist --pull always --rm -it alpine sh -c "set -xe; apk add --allow-untrusted --no-cache /dist/toxiproxy_*_linux_${ARCH}.apk; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-cli --version | grep \"toxiproxy-cli version ${VERSION}\""
+goreleaser release --rm-dist --skip-publish --skip-validate
+docker run -v $(PWD)/dist:/dist --pull always --rm -it ubuntu bash -c "set -xe; dpkg -i /dist/toxiproxy_*_linux_${ARCH}.deb; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-server --version ; /usr/bin/toxiproxy-cli --version ; /usr/bin/toxiproxy-cli --version | grep -o -e 'toxiproxy-cli version ${VERSION}'"
+docker run -v $(PWD)/dist:/dist --pull always --rm -it centos bash -c "set -xe; yum install -y /dist/toxiproxy_*_linux_${ARCH}.rpm; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-server --version ; /usr/bin/toxiproxy-cli --version | grep -o -e  \"toxiproxy-cli version ${VERSION}\""
+docker run -v $(PWD)/dist:/dist --pull always --rm -it alpine sh -c "set -xe; apk add --allow-untrusted --no-cache /dist/toxiproxy_*_linux_${ARCH}.apk; ls -1 /usr/bin/toxiproxy-*; /usr/bin/toxiproxy-server --version ; /usr/bin/toxiproxy-cli --version | grep -o -e  \"toxiproxy-cli version ${VERSION}\""
 
-tar -ztvf dist/toxiproxy_*_linux_amd64.tar.gz | grep toxiproxy-server
-tar -ztvf dist/toxiproxy_*_linux_amd64.tar.gz | grep toxiproxy-cli
+tar -ztvf dist/toxiproxy_*_linux_amd64.tar.gz | grep -o -e toxiproxy-server
+tar -ztvf dist/toxiproxy_*_linux_amd64.tar.gz | grep -o -e toxiproxy-cli
 
 goreleaser build --rm-dist --single-target --skip-validate --id server
-./dist/toxiproxy-server-* --help 2>&1 | grep "Usage of ./dist/toxiproxy-server"
+./dist/toxiproxy-server-* --help 2>&1 | grep -o -e "Usage of ./dist/toxiproxy-server"
+./dist/toxiproxy-server-* --version | grep -o -e "toxiproxy-server version ${VERSION}"
 
 goreleaser build --rm-dist --single-target --skip-validate --id client
-./dist/toxiproxy-cli-* --version | grep "toxiproxy-cli version ${VERSION}"
+./dist/toxiproxy-cli-* --help 2>&1 | grep -o -e "toxiproxy-cli - Simulate network and system conditions"
+./dist/toxiproxy-cli-* --version | grep -o -e "toxiproxy-cli version ${VERSION}"

cmd/server/server.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"math/rand"
 	"os"
 	"os/signal"
@@ -14,29 +15,32 @@ import (
 	"github.com/Shopify/toxiproxy/v2"
 )
 
-var (
-	host   string
-	port   string
-	config string
-)
+type cliArguments struct {
+	host         string
+	port         string
+	config       string
+	seed         int64
+	printVersion bool
+}
 
-func init() {
-	flag.StringVar(&host, "host", "localhost", "Host for toxiproxy's API to listen on")
-	flag.StringVar(&port, "port", "8474", "Port for toxiproxy's API to listen on")
-	flag.StringVar(&config, "config", "", "JSON file containing proxies to create on startup")
-	seed := flag.Int64("seed", time.Now().UTC().UnixNano(), "Seed for randomizing toxics with")
+func parseArguments() cliArguments {
+	result := cliArguments{}
+	flag.StringVar(&result.host, "host", "localhost",
+		"Host for toxiproxy's API to listen on")
+	flag.StringVar(&result.port, "port", "8474",
+		"Port for toxiproxy's API to listen on")
+	flag.StringVar(&result.config, "config", "",
+		"JSON file containing proxies to create on startup")
+	flag.Int64Var(&result.seed, "seed", time.Now().UTC().UnixNano(),
+		"Seed for randomizing toxics with")
+	flag.BoolVar(&result.printVersion, "version", false,
+		`print the version (default "false")`)
 	flag.Parse()
-	rand.Seed(*seed)
+
+	return result
 }
 
 func main() {
-	setupLogger()
-
-	server := toxiproxy.NewServer()
-	if len(config) > 0 {
-		server.PopulateConfig(config)
-	}
-
 	// Handle SIGTERM to exit cleanly
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGTERM)
@@ -45,7 +49,26 @@ func main() {
 		os.Exit(0)
 	}()
 
-	server.Listen(host, port)
+	cli := parseArguments()
+	run(cli)
+}
+
+func run(cli cliArguments) {
+	if cli.printVersion {
+		fmt.Printf("toxiproxy-server version %s\n", toxiproxy.Version)
+		return
+	}
+
+	setupLogger()
+
+	rand.Seed(cli.seed)
+
+	server := toxiproxy.NewServer()
+	if len(cli.config) > 0 {
+		server.PopulateConfig(cli.config)
+	}
+
+	server.Listen(cli.host, cli.port)
 }
 
 func setupLogger() {