Step 13.6: Define Database provider

index.ts

@@ -4,7 +4,6 @@ import { GraphQLModule } from '@graphql-modules/core';
 import http from 'http';
 import { app } from './app';
 import { origin, port } from './env';
-import { MyContext } from './context';
 
 import usersModule from './modules/users';
 import chatsModule from './modules/chats';
@@ -18,11 +17,6 @@ const server = new ApolloServer({
   schema: rootModule.schema,
   context: rootModule.context,
   subscriptions: rootModule.subscriptions,
-  formatResponse: (res: any, { context }: any) => {
-    context.db.release();
-
-    return res;
-  },
 });
 
 server.applyMiddleware({

modules/common/database.provider.ts

@@ -0,0 +1,26 @@
+import { Injectable, ProviderScope } from '@graphql-modules/di';
+import { OnResponse } from '@graphql-modules/core';
+import { Pool, PoolClient } from 'pg';
+
+@Injectable({
+  scope: ProviderScope.Session,
+})
+export class Database implements OnResponse {
+  private instance: PoolClient;
+
+  constructor(private pool: Pool) {}
+
+  async onRequest() {
+    this.instance = await this.pool.connect();
+  }
+
+  onResponse() {
+    if (this.instance) {
+      this.instance.release();
+    }
+  }
+
+  async getClient() {
+    return this.instance;
+  }
+}

modules/common/index.ts

@@ -1,8 +1,10 @@
 import { GraphQLModule } from '@graphql-modules/core';
 import { gql } from 'apollo-server-express';
 import { DateTimeResolver, URLResolver } from 'graphql-scalars';
+import { Pool } from 'pg';
 import { pool } from '../../db';
 import { Resolvers } from '../../types/graphql';
+import { Database } from './database.provider';
 
 const { PostgresPubSub } = require('graphql-postgres-subscriptions');
 
@@ -40,6 +42,13 @@ export default new GraphQLModule({
   name: 'common',
   typeDefs,
   resolvers,
+  providers: () => [
+    {
+      provide: Pool,
+      useValue: pool,
+    },
+    Database,
+  ],
   async context({ res, connection }) {
     let db;