Adds Signal (#5)

* Added test cases.

Co-authored-by: 李铭昕 <715557344@qq.com>

src/Signal.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of Hyperf.
+ *
+ * @link     https://www.hyperf.io
+ * @document https://hyperf.wiki
+ * @contact  group@hyperf.io
+ * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
+ */
+namespace Hyperf\Engine;
+
+use Hyperf\Engine\Contract\SignalInterface;
+use Swoole\Coroutine\System;
+
+class Signal implements SignalInterface
+{
+    public static function wait(int $signo, float $timeout = -1): bool
+    {
+        return System::waitSignal($signo, $timeout);
+    }
+}

tests/Cases/SignalTest.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of Hyperf.
+ *
+ * @link     https://www.hyperf.io
+ * @document https://hyperf.wiki
+ * @contact  group@hyperf.io
+ * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
+ */
+namespace HyperfTest\Cases;
+
+use Hyperf\Engine\Signal;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+class SignalTest extends AbstractTestCase
+{
+    public function testSignal()
+    {
+        $this->runInCoroutine(function () {
+            $res = Signal::wait(SIGUSR1, 1);
+            $this->assertFalse($res);
+
+            go(static function () {
+                sleep(1);
+                posix_kill(getmypid(), SIGUSR1);
+            });
+
+            $res = Signal::wait(SIGUSR1, 2);
+            $this->assertTrue($res);
+        });
+    }
+}