nvim/after/plugin/general.vim

let g:deoplete#enable_at_startup = 1
if !exists('g:deoplete#omni#input_patterns')
  let g:deoplete#omni#input_patterns = {}
endif

" <C-h>, <BS>: close popup and delete backword char.
"inoremap <expr><C-h> deoplete#smart_close_popup()."\<C-h>"
"inoremap <expr><BS>  deoplete#smart_close_popup()."\<C-h>"

inoremap <silent><expr> <TAB> 
      \ pumvisible() ? "\<C-n>" :
      \ <SID>check_back_space() ? "\<TAB>" :
      \ coc#refresh()
      "\ '\<C-x><C-o>'

function! s:check_back_space()
  let col = col('.') - 1
  return !col || getline('.')[col - 1]  =~ '\s'
endfunction
inoremap <silent><expr> <c-space> coc#refresh()