$ brew tap dart-lang/dart
$ brew install dart
错误处理
Cloning into '/usr/local/Homebrew/Library/Taps/dart-lang/homebrew-dart'... fatal: unable to access 'github.com/dart-lang/h…': Failed to connect to github.com port 443 after 75006 ms: Operation timed out
解决
1、www.ipaddress.com 拿到ip地址
2、sudo vi /etc/hosts
3、59.42.58.253 raw.githubusercontent.com
4、source /etc/hosts
