fix(core): Pg-promise de-initialization fix (#7417)

Github issue / Community forum post (link here to close automatically):

https://community.n8n.io/t/postgres-node-called-end-on-pool-more-than-once/30585/1

packages/nodes-base/nodes/Postgres/v1/PostgresV1.node.ts

@@ -323,7 +323,7 @@ export class PostgresV1 implements INodeType {
 
 					const db = pgp(config);
 					await db.connect();
-					pgp.end();
+					await db.$pool.end();
 				} catch (error) {
 					return {
 						status: 'Error',
@@ -412,15 +412,15 @@ export class PostgresV1 implements INodeType {
 
 			returnItems = wrapData(updateItems);
 		} else {
-			pgp.end();
+			await db.$pool.end();
 			throw new NodeOperationError(
 				this.getNode(),
 				`The operation "${operation}" is not supported!`,
 			);
 		}
 
-		// Close the connection
-		pgp.end();
+		// shuts down the connection pool associated with the db object to allow the process to finish
+		await db.$pool.end();
 
 		return [returnItems];
 	}