https://github.com/FIRHQ/fir-cli/blob/master/doc/install.md
- 官方 https://rubygems.org/
- 淘宝 https://ruby.taobao.org/
- Ruby China https://gems.ruby-china.org/
最近淘宝源一直没更新。。。建议切换到Ruby China
$ gem sources -a https://gems.ruby-china.org/ -r https://ruby.taobao.org/
$ gem sources -u
换回官方源
$ gem sources -a https://rubygems.org/ -r https://ruby.taobao.org/
$ gem sources -u
安装指定版本
gem install -v <version> <package>