ag -G .lua search_pattern

https://dingmingxin.github.io/blog/2016/05/05/%E7%A8%8B%E5%BA%8F%E5%91%98%E7%9A%84%E4%B8%83%E7%A7%8D%E6%AD%A6%E5%99%A8%E4%B9%8Bag/