I used ack for some time now grepping source code, yet I moved on to ripgrep since offers quiet more than than Grep und SourceCode-greps like SilverSearcher and Co. Plus it can mostly replace Grep and is mostly about 6x times faster (written In Rust). I am still astonished when I really get results instantly.
See here:
– https://blog.burntsushi.net/ripgrep/
– https://github.com/BurntSushi/ripgrep
This should be really installed on every server where you have to deal with source code.