time: test: Explicitly release Timer/Ticker resources

In the light of discovered memory leaks (see nexedi/pygolang!24),
it is better to explicitly make sure that resources allocated by every
test are explicitly released. Even though timers are released
automatically on their expiration, there is generally no guarantee that
the tests will finish after all timers are expired. And even more so for
Ticker - without explicit stop, the ticker continues to be active
forever.

So stop all created timers and tickers where we can in the tests.

/proposed-for-review-on nexedi/pygolang!26

golang/time_test.py

 # -*- coding: utf-8 -*-
-# Copyright (C) 2019  Nexedi SA and Contributors.
+# Copyright (C) 2019-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -20,8 +20,8 @@
 
 from __future__ import print_function, absolute_import
 
-from golang import select
-from golang import time
+from golang import select, func, defer
+from golang import time, sync
 from golang.golang_test import panics
 
 # all timer tests operate in dt units
@@ -65,6 +65,7 @@ def test_ticker_time():
 
 
 # test_timer verifies that Timer/Ticker fire as expected.
+@func
 def test_timer():
     # start timers at x5, x7 and x11 intervals an verify that the timers fire
     # in expected sequence. The times when the timers fire do not overlap in
@@ -73,15 +74,15 @@ def test_timer():
     tv = [] # timer events
     Tstart = time.now()
 
-    t23 = time.Timer(23*dt)
-    t5  = time.Timer( 5*dt)
+    t23 = time.Timer(23*dt);        defer(t23.stop)
+    t5  = time.Timer( 5*dt);        defer(t5 .stop)
 
     def _():
         tv.append(7)
         t7f.reset(7*dt)
-    t7f = time.Timer( 7*dt, f=_)
+    t7f = time.Timer( 7*dt, f=_);   defer(t7f.stop)
 
-    tx11 = time.Ticker(11*dt)
+    tx11 = time.Ticker(11*dt);      defer(tx11.stop)
 
     while 1:
         _, _rx = select(
@@ -108,19 +109,20 @@ def test_timer():
 
 
 # test_timer_misc, similarly to test_timer, verifies misc timer convenience functions.
+@func
 def test_timer_misc():
     tv = []
     Tstart = time.now()
 
-    c23 = time.after(23*dt)
-    c5  = time.after( 5*dt)
+    c23 = time.after(23*dt)         # cannot stop
+    c5  = time.after( 5*dt)         # cannot stop
 
     def _():
         tv.append(7)
         t7f.reset(7*dt)
-    t7f = time.after_func(7*dt, _)
+    t7f = time.after_func(7*dt, _); defer(t7f.stop)
 
-    cx11 = time.tick(11*dt)
+    cx11 = time.tick(11*dt)         # cannot stop
 
     while 1:
         _, _rx = select(
@@ -148,13 +150,14 @@ def test_timer_misc():
 
 
 # test_timer_stop verifies that .stop() cancels Timer or Ticker.
+@func
 def test_timer_stop():
     tv = []
 
-    t10 = time.Timer (10*dt)
-    t2  = time.Timer ( 2*dt)    # will fire and cancel t3, tx5
-    t3  = time.Timer ( 3*dt)    # will be canceled
-    tx5 = time.Ticker( 5*dt)    # will be canceled
+    t10 = time.Timer (10*dt);   defer(t10.stop)
+    t2  = time.Timer ( 2*dt);   defer(t2 .stop) # will fire and cancel t3, tx5
+    t3  = time.Timer ( 3*dt);   defer(t3 .stop) # will be canceled
+    tx5 = time.Ticker( 5*dt);   defer(tx5.stop) # will be canceled
 
     while 1:
         _, _rx = select(
@@ -180,9 +183,10 @@ def test_timer_stop():
 
 
 # test_timer_stop_drain verifies that Timer/Ticker .stop() drains timer channel.
+@func
 def test_timer_stop_drain():
-    t  = time.Timer (1*dt)
-    tx = time.Ticker(1*dt)
+    t  = time.Timer (1*dt);     defer(t.stop)
+    tx = time.Ticker(1*dt);     defer(tx.stop)
 
     time.sleep(2*dt)
     assert len(t.c)  == 1
@@ -196,8 +200,9 @@ def test_timer_stop_drain():
 
 
 # test_timer_reset_armed verifies that .reset() panics if called on armed timer.
+@func
 def test_timer_reset_armed():
     # reset while armed
-    t = time.Timer(10*dt)
+    t = time.Timer(10*dt);  defer(t.stop)
     with panics("Timer.reset: the timer is armed; must be stopped or expired"):
         t.reset(5*dt)