fix: add subscriptions and closeHandler nil check

README.md

@@ -1,2 +1,42 @@
 # nacl
+
 Client helper for NATS/STAN
+
+## examples
+
+connect to NATS
+
+```go
+package main
+
+import (
+    "fmt"
+    "github.com/jar3b/grawt"
+    "github.com/jar3b/nacl"
+    "github.com/kelseyhightower/envconfig"
+)
+
+func main() {
+    // get params
+    conf := config.NewConfig()
+
+	// init waiter (github.com/jar3b/grawt)
+	var waiter = grawt.NewWaiter()
+
+	// init nats
+	var subscriptions []*nacl.NatsSubscription
+	if err := nacl.SetupNats(conf.Nats.Host, conf.Nats.Port, conf.Nats.User, conf.Nats.Pass,
+		// handler called before app closed
+        // we need to terminate sub's properly and sometimes doing another actions (finalizers)
+        waiter.AddCloseHandler(func() {
+			nacl.FinalizeNats(&subscriptions)
+		}, false),
+	); err != nil {
+		waiter.Halt(fmt.Errorf("cannot connect to nats: %v", err))
+	}
+	defer nacl.NatsClient.Close()
+	
+    // here we add some subscriptions and wait (using blocking call)
+    // ...
+}
+```

nacl.go

@@ -34,7 +34,9 @@ func SetupNats(host string, port int, user string, pass string, closeHandler *gr
 	NatsClient, err = nats.Connect(
 		connectionString,
 		nats.ClosedHandler(func(conn *nats.Conn) {
-			closeHandler.Halt(nil)
+			if closeHandler != nil {
+				closeHandler.Halt(nil)
+			}
 		}),
 		nats.MaxReconnects(5),
 		nats.ReconnectWait(time.Second*2),
@@ -68,8 +70,11 @@ func FinalizeStan(subscriptions *[]Subscription) error {
 	if StanClient == nil {
 		return fmt.Errorf("stan client is not initialized")
 	}
-	for _, subscription := range *subscriptions {
-		_ = subscription.Unsubscribe()
+
+	if subscriptions != nil {
+		for _, subscription := range *subscriptions {
+			_ = subscription.Unsubscribe()
+		}
 	}
 
 	if err := StanClient.Close(); err != nil {
@@ -83,8 +88,11 @@ func FinalizeNats(subscriptions *[]*NatsSubscription) error {
 	if NatsClient == nil {
 		return fmt.Errorf("stan client is not initialized")
 	}
-	for _, subscription := range *subscriptions {
-		_ = subscription.Unsubscribe()
+
+	if subscriptions != nil {
+		for _, subscription := range *subscriptions {
+			_ = subscription.Unsubscribe()
+		}
 	}
 
 	NatsClient.Close()