After searched and reviewed some similar solutions like that of Gulp and Grunt (many solutions are from NodeJS community), I think writing a universal command line tool with Go might be cool.
The advantages of this command is that it does not need any external dependencies and the precompiled binary can run directly on linux and macOS. It is useful not only for running dev server with `go run server.go` or `python server.py` but also when you want to rebuild your go project after any changes of source code. It is designed to be extremely simple and I have already been enjoying it during the development of itself!
Although it is lack of unit tests yet, I think it might be good for you to try it out now :)
I've downloaded it given it a shot and now realize I actually like it a lot more than entr because I don't have to have development environment instructions in my Deploy readme, I can commit the .wu.json file. :) Much better to have that in version control.