feat(client): add custom usage message (#152)

Co-authored-by: Cameron Meissner <cameissner@microsoft.com>

Author: cameronmeissner

client/cmd/client/main.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/Azure/aks-secure-tls-bootstrap/client/internal/bootstrap"
+	"github.com/Azure/aks-secure-tls-bootstrap/client/internal/build"
 	"github.com/Azure/aks-secure-tls-bootstrap/client/internal/kubeconfig"
 	"github.com/Azure/aks-secure-tls-bootstrap/client/internal/log"
 	"github.com/Azure/aks-secure-tls-bootstrap/client/internal/telemetry"
@@ -44,6 +45,12 @@ func init() {
 	flag.BoolVar(&config.InsecureSkipTLSVerify, "insecure-skip-tls-verify", false, "skip TLS verification when connecting to the control plane")
 	flag.BoolVar(&config.EnsureAuthorizedClient, "ensure-authorized", false, "ensure the specified kubeconfig contains an authorized clientset before bootstrapping")
 	flag.DurationVar(&config.Deadline, "deadline", 0, "the deadline within which bootstrapping must succeed")
+
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage of %s - %s:\n", os.Args[0], build.GetVersion())
+		flag.PrintDefaults()
+	}
+
 	flag.Parse()
 }