Trying to reserve a connection without previously executing any sql hangs indefinitely.

This does not happen unless fetch_types is set to false which means no connections are attempted before the reserve. If you leave fetch_types alone, or perform another sql opteration first, it works.

Using the latest version:

const postgres = require('postgres');

async function main() {
	const sql = postgres({
		host: '127.0.0.1',
		port: 5432,
		user: 'postgres',
		password: 'postgres',
		database: 'postgres',
		fetch_types: false
	});

	console.log('Starting');
	const reserved = await sql.reserve();
	console.log(await reserved`select 1`);
	console.log('done');
	reserved.release();
}

main();

Start with the supplied JavaScript reproduction, focusing on sql.reserve(), fetch_types: false, and the reserved tagged select query. Confirm the hang before changing anything, then trace the reserve path and add or run a regression check showing that reservation resolves, select 1 returns, and reserved.release() completes.