Fix memory leak when using socket timeout and keepalive agent (#694)

Fixes #690

source/utils/timed-out.js

@@ -82,11 +82,16 @@ module.exports = (request, delays, options) => {
 	}
 
 	if (delays.socket !== undefined) {
-		request.setTimeout(delays.socket, () => {
+		const socketTimeoutHandler = () => {
 			timeoutHandler(delays.socket, 'socket');
-		});
+		};
+
+		request.setTimeout(delays.socket, socketTimeoutHandler);
 
-		cancelers.push(() => request.setTimeout(0));
+		// `request.setTimeout(0)` causes a memory leak.
+		// We can just remove the listener and forget about the timer - it's unreffed.
+		// See https://github.com/sindresorhus/got/issues/690
+		cancelers.push(() => request.removeListener('timeout', socketTimeoutHandler));
 	}
 
 	if (delays.lookup !== undefined && !request.socketPath && !net.isIP(hostname || host)) {

test/timeout.js

@@ -473,3 +473,21 @@ test('socket timeout is canceled on error', async t => {
 	// Wait a bit more to check if there are any unhandled errors
 	await delay(10);
 });
+
+test('no memory leak when using socket timeout and keepalive agent', async t => {
+	const promise = got(s.url, {
+		agent: keepAliveAgent,
+		timeout: {socket: requestDelay * 2}
+	});
+
+	let socket;
+	promise.on('request', request => {
+		request.on('socket', () => {
+			socket = request.socket;
+		});
+	});
+
+	await promise;
+
+	t.is(socket.listenerCount('timeout'), 0);
+});