解决fatal: unable to access 'https://github.com/homebrew/brew/':的问题

本地安装了Homebrew，执行brew -v 可以正常执行

Homebrew >=2.5.0 (shallow or no git repository)
Homebrew/homebrew-core N/A

但是执行Homebrew更新update 总是报错，brew update

fatal: unable to access 'https://github.com/Homebrew/brew/': LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443 

解决方案：
依次执行以下命令就可以正常update Homebrew

git config --global --unset http.proxy 
git config --global --unset https.proxy