brew update卡住的解决方法：
将官方源替换为国内镜像
Homebrew源代码仓库
cd “$(brew --repo)”
git remote set-url origin https://mirrors.ustc.edu.cn/brew.git
Homebrew Bottles
echo ‘export HOMEBREW_BOTTLE_DOMAIN=https://mirrors.ustc.edu.cn/homebrew-bottles’ >> ~/.zshrc source ~/.zshrc
brew core
cd “$(brew --repo)/Library/Taps/homebrew/homebrew-core”
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git
brew cast
cd “$(brew --repo)”/Library/Taps/homebrew/homebrew-cask
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-cask.git