安装
SDK官网获取地址 https://dart.cn/get-dart
Mac安装命令
$ brew tap dart-lang/dart
$ brew install dart
在执行命令brew tap dart-lang/dart的时候提示
$ brew tap dart-lang/dart
==> Tapping dart-lang/dart
Cloning into '/usr/local/Homebrew/Library/Taps/dart-lang/homebrew-dart'...
fatal: unable to access 'https://github.com/dart-lang/homebrew-dart/': Failed to connect to github.com port 443: Operation timed out
Error: Failure while executing; `git clone https://github.com/dart-lang/homebrew-dart /usr/local/Homebrew/Library/Taps/dart-lang/homebrew-dart` exited with 128.
github链接 https://github.com/dart-lang/homebrew-dart
这就得让github能下载或者提升github的下载速度了，怎么解决从github下载资源慢？
方法一：通过代理的方式，添加临时变量，一步搞定，如果你有代理，那么一定是这么玩的。 因为我有代理所以，用此方法直接搞定，不用往下看了。
export ALL_PROXY=socks5://127.0.0.1:1080
https://www.zhihu.com/question/276143842