brew update ,Error: /usr/local is not writable. You should change the ownership 解決方法

ターミナルで$brew update ができなかったので、メモ　答え書いてあるけど

$ brew update 
Error: /usr/local is not writable. You should change the ownership
and permissions of /usr/local back to your user account: sudo chown -R $(whoami) /usr/local

$sudo chown -R $(whoami) /usr/local こちらでpermissionを変更してあげれば解決です