Failed golang tests

Sometimes i catch this errors
https://github.com/Smolevich/roadrunner/commit/14dac9be74e95185a3bf6c724559de5349a1a6e0/checks?check_suite_id=278333602

https://github.com/Smolevich/roadrunner/runs/272166358

https://github.com/Smolevich/roadrunner/runs/272166358

Сan someone say why such errors occur?