change constructor param of gson serializer

Author: Wernerson

clients/graphql-kotlin-client-gson/src/main/kotlin/com/expediagroup/graphql/client/gson/GraphQLClientGsonSerializer.kt

@@ -21,7 +21,7 @@ import com.expediagroup.graphql.client.types.GraphQLClientError
 import com.expediagroup.graphql.client.types.GraphQLClientRequest
 import com.expediagroup.graphql.client.types.GraphQLClientResponse
 import com.expediagroup.graphql.client.types.GraphQLClientSourceLocation
-import com.google.gson.Gson
+import com.google.gson.GsonBuilder
 import com.google.gson.JsonArray
 import com.google.gson.JsonParser.parseString
 import com.google.gson.reflect.TypeToken
@@ -51,7 +51,7 @@ data class GsonGraphQLResponse<T>(
  * Gson based GraphQL request/response serializer.
  */
 class GraphQLClientGsonSerializer(
-    private val gson: Gson = Gson()
+    gsonBuilder: GsonBuilder = GsonBuilder().serializeNulls()
 ) : GraphQLClientSerializer {
 
     private val typeCache = ConcurrentHashMap<KClass<*>, Type>()
@@ -61,6 +61,8 @@ class GraphQLClientGsonSerializer(
             TypeToken.getParameterized(GsonGraphQLResponse::class.java, type.java).type
         }
 
+    private val gson = gsonBuilder.create()
+
     override fun serialize(request: GraphQLClientRequest<*>): String = gson.toJson(request)
 
     override fun serialize(requests: List<GraphQLClientRequest<*>>): String = gson.toJson(requests)

clients/graphql-kotlin-client-gson/src/test/kotlin/com/expediagroup/graphql/client/gson/GraphQLClientGsonSerializerTest.kt

@@ -19,16 +19,14 @@ package com.expediagroup.graphql.client.gson
 import com.expediagroup.graphql.client.gson.data.*
 import com.expediagroup.graphql.client.gson.data.enums.TestEnum
 import com.expediagroup.graphql.client.gson.data.polymorphicquery.SecondInterfaceImplementation
-import com.google.gson.GsonBuilder
 import com.google.gson.JsonParser
 import org.junit.jupiter.api.Test
 import java.util.*
 import kotlin.test.assertEquals
 
 class GraphQLClientGsonSerializerTest {
 
-    private val gson = GsonBuilder().serializeNulls().create()
-    private val serializer = GraphQLClientGsonSerializer(gson)
+    private val serializer = GraphQLClientGsonSerializer()
 
     @Test
     fun `verify we can serialize GraphQLClientRequest`() {