add WithNameServerDomain for producer opt (#438)

Co-authored-by: quxiaolong <quxiaolong@zhirens.com>
diff --git a/producer/option.go b/producer/option.go
index ae5d51f..97a480e 100644
--- a/producer/option.go
+++ b/producer/option.go
@@ -70,6 +70,13 @@
 	}
 }
 
+// WithNameServerDomain set NameServer domain
+func WithNameServerDomain(nameServerUrl string) Option {
+	return func(opts *producerOptions) {
+		opts.NameServerDomain = nameServerUrl
+	}
+}
+
 // WithNamespace set the namespace of producer
 func WithNamespace(namespace string) Option {
 	return func(opts *producerOptions) {