fix(graphql): register extension only for not release mode and not al…

…ready registered

packages/graphql/lib/src/graphql_client.dart

@@ -9,6 +9,9 @@ import 'package:graphql/src/cache/cache.dart';
 
 import 'package:graphql/src/core/fetch_more.dart';
 
+/// Flag to register extension only once
+bool _isExtensionRegistered = false;
+
 /// Universal GraphQL Client with configurable caching and [link][] system.
 /// modelled after the [`apollo-client`][ac].
 ///
@@ -35,14 +38,19 @@ class GraphQLClient implements GraphQLDataProxy {
           cache: cache,
           alwaysRebroadcast: alwaysRebroadcast,
         ) {
-    // Register the extension to expose the cache to the devtools
-    registerExtension(
-      'ext.graphql.getCache',
-      (method, parameters) async {
-        return ServiceExtensionResponse.result(
-            jsonEncode({'value': this.cache.store.toMap()}));
-      },
-    );
+    const releaseMode = bool.fromEnvironment('dart.vm.product');
+    // Register extension for not in release mode and not already registered
+    if (!releaseMode && !_isExtensionRegistered) {
+      // Register the extension to expose the cache to the devtools
+      registerExtension(
+        'ext.graphql.getCache',
+        (method, parameters) async {
+          return ServiceExtensionResponse.result(
+              jsonEncode({'value': this.cache.store.toMap()}));
+        },
+      );
+      _isExtensionRegistered = true;
+    }
   }
 
   /// The default [Policies] to set for each client action