mac osx升级ruby

# 安装rvm

$ curl -sSL https://raw.githubusercontent.com/rvm/rvm/master/binscripts/rvm-installer | bash -s stable

# 添加rvm到系统path

$source/Users/xxx/.rvm/scripts/rvm

# 列出安装包

$ rvm list known

# 安装ruby，如果安装失败，再执行一次。我执行了三次才成功

$ rvm install ruby-2.6.3

# 安装成功

$ ruby -v

# 输出：ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin16]