Modify time first, round after (and strip additional precision).

[dmitshur]

DO NOT MERGE. Let's discuss this change first.

I've noticed that TestDo_rateLimit_noNetworkCall test fails on Go master with the following error:

--- FAIL: TestDo_rateLimit_noNetworkCall (0.00s)
	github_test.go:549: rateLimitErr rate reset = 2017-02-25 01:49:01 +0000 UTC, want 2017-02-25 01:49:01 +0000 UTC m=+60.206993003

(Source: https://travis-ci.org/google/go-github/jobs/205180544.)

This is due to changes in Go 1.9 to perform monotonic elapsed time measurements. See golang/go#12914 and https://golang.org/design/12914-monotonic for full details.

Make the test pass by modifying time first, round after, and strip the monotonic clock reading by using AddDate(0, 0, 0). Doing that eliminates the unwanted additional monotonic precision from wanted time, making the expected time equality true.

This is also related to an open issue golang/go#18991. Depending on the outcome there, this PR could be simplified not to need AddDate(0, 0, 0).

I just wanted to get this PR created for visibility. We can discuss the potential fix, and wait on Go 1.9 to get closer to release before actually merging this, because there may be additional changes that would render this change overly complex or unnecessary.

[dmitshur]

Worth noting, the reorder of Round(time.Second) and Add(time.Minute) actually has no effect at all, I did it just because the new order seemed more readable and logical to me. It was also more consistent with the comment.

The addition of AddDate(0, 0, 0) is the only thing that has an effect (in current Go master only, not in Go 1.8).

[dmitshur]

After golang/go@6c85fb0, this change to use AddDate(0, 0, 0) is no longer neccessary.

I still like the re-order of Round(time.Second) and Add(time.Minute), so maybe we can keep that. I'll update the PR.

[gmlewis]

I like the reorder too.

[dmitshur]

Actually, I think it's better to just close this PR, since the scope has changed too much. I'll just open a new PR for the small refactor, and reference this. We can close this PR since it's no longer needed.