How can I get <cword> in command mode using lua

Neovim
#1 
nnoremap <expr> <Leader>s* ':<C-u>%s/\<' . expand('<cword>') . '\>//g<Left><Left>'

How this keymap is converted to lua

#2

I have solved it myself：

keymap("n", "<Leader>sg", [[':<C-u>%s/\<' . expand('<cword>') . '\>//g<Left><Left>']], { noremap = true, silent = false, expr = true })