feat(NA): enclose wsclient creation inside addGraphQLWS function.

src/helpers.ts

@@ -1,4 +1,4 @@
-import { SubscriptionClient } from './client';
+import { SubscriptionClient, ClientOptions } from './client';
 import { ExecutionResult } from 'graphql';
 
 /**
@@ -22,7 +22,12 @@ export function addGraphQLSubscriptions(networkInterface: any, wsClient: Subscri
   });
 }
 
-export function addGraphQLWS(networkInterface: any, wsClient: SubscriptionClient): any {
+export function addGraphQLWS(networkInterface: any, wsClientOptions: ClientOptions): any {
+  if (typeof networkInterface._uri !== 'string') {
+    throw new Error('Given networkInterface should have an uri defined to config the websocket.');
+  }
+
+  const wsClient = new SubscriptionClient(networkInterface._uri, wsClientOptions);
   return Object.assign(addGraphQLSubscriptions(networkInterface, wsClient), {
     query(request: any): Promise<ExecutionResult> {
       return wsClient.query(request);