Adds a small test to catch issues with deadlocks

[davidporter-id-au]

It's quite easy to call the getters on tasks in this function and cause a deadlock. Ensuring complete coverage on this branch to prevent this.

[Groxx]

Since a deadlock won't panic, I've done this in the past:

done := make(chan struct{})
go func() {
  defer close(done)
  deadlocky()
}()
select {
case <-done:
case <-time.After(time.Second): t.Error("timed out == deadlock")
}

fast enough to be practical, without waiting for a full minute or whatever for the normal whole-package test timeout.

[davidporter-id-au]

while I appreciate that makes for a better performing test, it... feels slightly overspecialised with the benefit of hindsight to look exclusively for deadlocks, rather than just checking the path entirely (though, I suppose it would catch a panic all the same).

It looks like there'll be a new testing.T method SetTimeout(d time.Duration) coming soon which should do exactly this and - imho, is a lot less noisy (golang/go#48157)

I don't feel super strongly about it, but I'm wary about one-off testing infra setups such as this in that their complexity might dissuade people to maintain / think about them

[Groxx]

SetTimeout would be kinda nice, yea.

I mean more that this wasn't a panic symptom, and "does not panic" on its own is not all that useful of an assertion anyway, since a panicking test is already a test failure. The fact that it's in use seems to imply there's something panic-sensitive about the code in question, and AFAIK there is not.

[coveralls]

Pull Request Test Coverage Report for Build 01871f21-31ef-46ee-afd1-732d9cae568d

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 128 unchanged lines in 11 files lost coverage.
• Overall coverage decreased (-0.04%) to 57.075%

---

Files with Coverage Reduction	New Missed Lines	%
common/membership/hashring.go	2	83.54%
common/task/weightedRoundRobinTaskScheduler.go	2	89.12%
common/util.go	2	52.31%
service/matching/matcher.go	2	91.46%
service/history/task/fetcher.go	3	91.75%
service/history/task/transfer_standby_task_executor.go	4	87.66%
common/persistence/statsComputer.go	6	93.57%
common/persistence/serialization/parser.go	12	62.41%
common/persistence/serialization/thrift_decoder.go	12	53.06%
common/persistence/sql/workflowStateMaps.go	31	81.25%

Totals
Change from base Build 0186f1b3-9b0c-4754-b0ff-0eb624d0ee79:	-0.04%
Covered Lines:	85223
Relevant Lines:	149317

---

💛 - Coveralls

[Groxx]

useful test either way, comments are just comments and not in any way meant as a requirement :)