use direct bindings for coc autocomplete

dot-config/nvim/keys/bindings.vim

@@ -98,16 +98,19 @@ function! FernInit() abort
 endfunction
 
 " use TAB to autocomplete w/ coc
-inoremap <silent><expr> <TAB>
-      \ pumvisible() ? "\<C-n>" :
-      \ <SID>check_back_space() ? "\<TAB>" :
-      \ coc#refresh()
-inoremap <expr><S-TAB> pumvisible() ? "\<C-p>" : "\<C-h>"
-
-function! s:check_back_space() abort
-  let col = col('.') - 1
-  return !col || getline('.')[col - 1]  =~# '\s'
-endfunction
+" inoremap <silent><expr> <TAB>
+"       \ pumvisible() ? "\<C-n>" :
+"       \ <SID>check_back_space() ? "\<TAB>" :
+"       \ coc#refresh()
+" inoremap <expr><S-TAB> pumvisible() ? "\<C-p>" : "\<C-h>"
+
+" function! s:check_back_space() abort
+"   let col = col('.') - 1
+"   return !col || getline('.')[col - 1]  =~# '\s'
+" endfunction
+
+inoremap <expr> <Tab> coc#pum#visible() ? coc#pum#next(1) : "\<Tab>"
+inoremap <expr> <S-Tab> coc#pum#visible() ? coc#pum#prev(1) : "\<S-Tab>"
 
 " Use `:Format` to format current buffer
 command! -nargs=0 Format :call CocAction('format')