Describes the cause and action for error messages.
Error Message(English)：
unable to connect to github.com proxy
gitコマンドのプロトコルをhttpsに固定する(社内環境でよくある話) - Qiita
https://qiita.com/nntsugu/items/38dc49a47d1b658325e8
GitでProxyの設定を行ってエラー回避する方法 | gitの使い方講座
https://git-manual.net/git-proxy-error/
Unable to Connect to GitHub.com For Cloning - Stack Overflow
https://stackoverflow.com/questions/16298986/unable-to-connect-to-github-com-for-cloning
Failed to connect to github 443
https://stackoverflow.com/questions/29333319/failed-to-connect-to-github-443
could not resolve host github.com error while cloning remote ...
https://stackoverflow.com/questions/20370294/could-not-resolve-host-github-com-error-while-cloning-r・・・
GitHub - failed to connect to github 443 windows/ Failed to ...
https://stackoverflow.com/questions/18356502/github-failed-to-connect-to-github-443-windows-failed-t・・・
pull command error : Failed connect to github.com:8080
https://stackoverflow.com/questions/5102361/pull-command-error-failed-connect-to-github-com8080
GitHub - Gitでcloneした際のプロキシ設定に関するエラーが発生する ...
https://teratail.com/questions/120502
Unable to access repository over HTTPS ・ Issue #3713 ... - GitHub
https://github.com/desktop/desktop/issues/3713