How to integrate grep or rg with vim?

[Masber]

Dear fzf community,

I am learning how to configure vim and trying to customize my vim-fzf experience...
I would like to know how to integrate grep/rg with fzf in vim.

I tried the following which does not work:

nnoremap <Leader>sg :call fzf#run({'source': 'rg', 'sink': 'e', 'down': '40%'})<CR>

Any advice?

thank you very much