fix unit test error for framework

Author: inhere

test/unit/CoTest.php

@@ -26,7 +26,7 @@ class CoTest extends TestCase
 {
  /**
  */
- public function tearDown()
+ public function tearDown(): void
  {
  Context::getWaitGroup()->wait();
  }

test/unit/TimerTest.php

@@ -36,7 +36,7 @@ class TimerTest extends TestCase
 
  /**
  */
- public function setUp()
+ public function setUp(): void
  {
  Context::set(TestContext::new());
  }