WaterFlow is a Go program that provides community-maintained free and open-source hydrology tools, implementing state-of-the-art algorithms found in the literature. WaterFlow tools aim to be API-compatible with ESRI Hydrology toolset but do not necessarily guarantee to produce exactly the same output in the pixel/cell level as ESRI tools.
Why do you think that https://github.com/twpayne/go-geom is a good alternative to waterflow