doc: update readme to use os-specific path separator

[youming-lin]

[andrii-zakurenyi]

Hi @youming-lin Can you please update the code to use filepath.Base() instead of that custom for loop: https://pkg.go.dev/path/filepath#Base

Something like:

return filepath.Base(file) + ":" + strconv.Itoa(line)

[youming-lin]

@andrii-zakurenyi Absolutely! That's what I ended up using as well after a bit more Googling 😃

I've updated the PR, please check again.