Emit timeout errors as soon as possible

Fixes #997

Author: szmarczak

source/utils/timed-out.ts

@@ -33,21 +33,12 @@ export default (request: ClientRequest, delays: Delays, options: TimedOutOptions
 	const {once, unhandleAll} = unhandler();
 
 	const addTimeout = <T extends any[]>(delay: number, callback: (delay: number, ...args: T) => void, ...args: T): (typeof noop) => {
-		// Event loop order is timers, poll, immediates.
-		// The timed event may emit during the current tick poll phase, so
-		// defer calling the handler until the poll phase completes.
-		let immediate: NodeJS.Immediate;
-		const timeout: NodeJS.Timeout = setTimeout(() => {
-			// @ts-ignore https://github.com/microsoft/TypeScript/issues/26113
-			immediate = setImmediate(callback, delay, ...args);
-			immediate.unref?.();
-		}, delay);
+		const timeout = setTimeout(callback, delay, ...args) as unknown as NodeJS.Timeout;
 
 		timeout.unref?.();
 
 		const cancel = (): void => {
 			clearTimeout(timeout);
-			clearImmediate(immediate);
 		};
 
 		cancelers.push(cancel);

test/timeout.ts

@@ -10,7 +10,7 @@ import delay = require('delay');
 import CacheableLookup from 'cacheable-lookup';
 import {Handler} from 'express';
 import pEvent = require('p-event');
-import got from '../source';
+import got, {TimeoutError} from '../source';
 import timedOut from '../source/utils/timed-out';
 import slowDataStream from './helpers/slow-data-stream';
 import {GlobalClock} from './helpers/types';
@@ -622,3 +622,15 @@ test.serial('cancelling the request removes timeouts', withServer, async (t, ser
 
 	await delay(1000);
 });
+
+test('timeouts are emitted ASAP', async t => {
+	const timeout = 500;
+	const marginOfError = 100;
+
+	const error: TimeoutError = await t.throwsAsync(got('http://192.0.2.1/test', {
+		retry: 0,
+		timeout
+	}), TimeoutError);
+
+	t.true(error.timings.phases.total! < (timeout + marginOfError));
+});