The e2e tests can be flaky due to various tests mutating shared mutable
fixtures, causing non-deterministic behavior depending on the test set, order,
etc.
For example, `configTLS` is mutated in at least two tests in such a way that the
config is potentially invalidated for any subsequent test running in the same
process (e.g. by setting the `enableV2` field). This particular example caused
a substantial amount of confusion diagnosing the new test introduced for
https://github.com/etcd-io/etcd/pull/12370.
Independent tests should not share mutable state unless deliberately. This patch
refactors the e2e test config fixtures to safeguard against these problems by
replacing the package variables (which cannot easily be made immutable) with
functions that return new instances.
Update to Go 1.12.5 testing. Remove deprecated unused and gosimple
pacakges, and mask staticcheck 1006. Also, fix unconvert errors related
to unnecessary type conversions and following staticcheck errors:
- remove redundant return statements
- use for range instead of for select
- use time.Since instead of time.Now().Sub
- omit comparison to bool constant
- replace T.Fatal and T.Fatalf in tests with T.Error and T.Fatalf respectively because the goroutine calls T.Fatal must be called in the same goroutine as the test
- fix error strings that should not be capitalized
- use sort.Strings(...) instead of sort.Sort(sort.StringSlice(...))
- use he status code of Canceled instead of grpc.ErrClientConnClosing which is deprecated
- use use status.Errorf instead of grpc.Errorf which is deprecated
Related #10528#10438
