办法 1：按住 control + c 勾销本次更新操作
➜ ~ brew install composer
Updating Homebrew...
^C按住 control + c 之后命令行会显示 ^C，就代表曾经勾销了 Updating Homebrew 操作
大略不到 1 秒钟之后就会去执行咱们真正须要的安装操作了
➜ ~ brew install composer
Updating Homebrew...
^C==> Satisfying dependencies
==> Downloading https://getcomposer.org/download/1.7.2/composer.phar
...