配置下国内源
gem sources -r https://rubygems.org/ -a https://gems.ruby-china.com/
如果网络错误 更换下面地址
gem sources --remove https://rubygems.org
source https://rubygems.org not present in cache
gem sources --add http://rubygems.org
https://rubygems.org is recommended for security over http://rubygems.org
Do you want to add this insecure source? [yn] y
source http://rubygems.org already present in the cache