testing: Long Tests on macos is broken

[hyangah]

It remained broken since the commit c705adf but not sure if this was caused by the change or something else.

The first failure: https://github.com/golang/vscode-go/actions/runs/248716238
The latest failure: https://github.com/golang/vscode-go/runs/1112740681?check_suite_focus=true
The last success: https://github.com/golang/vscode-go/runs/1096780198?check_suite_focus=true

[hyangah]

So far the difference I noticed was the vscode version, and most tests took slower. But that doesn't seem to be the culprit. From the failed log case, we are seeing that the test process just hung after all 80 tests passed. We need to figure out what this process is waiting fo.

...

2020-09-10T20:54:11.5923530Z �[0m  GuessPackageNameFromFile Tests�[0m
2020-09-10T20:54:11.5924530Z   �[32m  ✓�[0m�[90m package name from main file�[0m
2020-09-10T20:54:11.5968450Z   �[32m  ✓�[0m�[90m package name from dirpath�[0m
2020-09-10T20:54:11.5968680Z 
2020-09-10T20:54:11.5969330Z   �[32m  ✓�[0m�[90m package name from test file�[0m
2020-09-10T20:54:11.5969450Z 
2020-09-10T20:54:11.5970120Z �[92m �[0m�[32m 80 passing�[0m�[90m (1m)�[0m
2020-09-10T20:54:11.5970230Z 
2020-09-10T21:08:08.4252310Z ##[error]The operation was canceled.
2020-09-10T21:08:08.4391850Z Post job cleanup.
2020-09-10T21:08:08.5853790Z [command]/usr/local/bin/git version
2020-09-10T21:08:08.5938530Z git version 2.28.0
2020-09-10T21:08:08.5991420Z [command]/usr/local/bin/git config --local --name-only --get-regexp core\.sshCommand

The last success: vscode-1.48.2 raw log

The first failure: vscode-1.49.0 raw log