fix a bug where AdvanceNext unlocks twice

[edwingeng]

How to reproduce:

func TestQuartz_AdvanceNext(t *testing.T) { clock := quartz.NewMock(t) clock.AdvanceNext() time.Sleep(time.Second) } 

Output:

fatal error: sync: unlock of unlocked mutex goroutine 19 [running]: sync.fatal({0x86845ba?, 0x86dd020?}) runtime/panic.go:1031 +0x18 sync.(*Mutex).unlockSlow(0xc0000f2010, 0xffffffff) sync/mutex.go:231 +0x35 sync.(*Mutex).Unlock(...) sync/mutex.go:225 github.com/coder/quartz.(*Mock).advanceLocked(0xc0000f2000, {{0x86f6058?, 0xc0000a6820?}, 0xc00008e310?}) github.com/coder/quartz/mock.go:299 +0x1a7 created by github.com/coder/quartz.(*Mock).AdvanceNext in goroutine 18 github.com/coder/quartz/mock.go:355 +0x28b goroutine 1 [chan receive]: testing.(*T).Run(0xc0000a6680, {0x8681fa8?, 0xfb73180009ab50?}, 0x86f2f68) testing/testing.go:1751 +0x3ab testing.runTests.func1(0xc0000a6680) testing/testing.go:2168 +0x37 testing.tRunner(0xc0000a6680, 0xc00009ac70) testing/testing.go:1690 +0xf4 testing.runTests(0xc00009e180, {0x87d5d60, 0x9, 0x9}, {0x85bd7d0?, 0x85bd43a?, 0x87da620?}) testing/testing.go:2166 +0x43d testing.(*M).Run(0xc0000ac0a0) testing/testing.go:2034 +0x64a main.main() _testmain.go:63 +0x9b goroutine 18 [sleep]: time.Sleep(0x3b9aca00) runtime/time.go:300 +0xf2 github.com/coder/quartz_test.TestQuartz_AdvanceNext(0xc0000a6820?) github.com/coder/quartz/mock_test.go:326 +0x2f testing.tRunner(0xc0000a6820, 0x86f2f68) testing/testing.go:1690 +0xf4 created by testing.(*T).Run in goroutine 1 testing/testing.go:1743 +0x390 exit status 2 

Cause:

https://github.com/coder/quartz/blob/7f10f7fd6925130f6548710df54992e832cfce2d/mock.go#L348 

[spikecurtis]

Thanks! Nice catch.