Merge pull request #17753 from leizha/pool

[pg] Pool.end() accepts an optional callback param

types/pg/index.d.ts

@@ -71,7 +71,7 @@ export declare class Pool extends events.EventEmitter {
     connect(): Promise<Client>;
     connect(callback: (err: Error, client: Client, done: () => void) => void): void;
 
-    end(): Promise<void>;
+    end(callback?: () => void): Promise<void>;
 
     query(queryStream: QueryConfig & stream.Readable): stream.Readable;
     query(queryTextOrConfig: string | QueryConfig): Promise<QueryResult>;

types/pg/pg-tests.ts

@@ -74,3 +74,8 @@ pool.connect((err, client, done) => {
 pool.on('error', (err, client) => {
   console.error('idle client error', err.message, err.stack)
 })
+
+pool.end();
+pool.end(() => {
+    console.log("pool is closed");
+});