init.lua

    -- nvim cmp
    use { 'hrsh7th/cmp-nvim-lsp'}
    use { 'hrsh7th/cmp-buffer' }
    use { 'hrsh7th/cmp-path'}
    use { 'hrsh7th/cmp-cmdline'}
    use { 'quangnguyen30192/cmp-nvim-ultisnips' }
    use { 'hrsh7th/nvim-cmp', 
      config = function ()
         -- Setup nvim-cmp.
        local cmp = require'cmp'
        cmp.setup({
          snippet = {
            -- REQUIRED - you must specify a snippet engine
            expand = function(args)
              vim.fn["vsnip#anonymous"](args.body) -- For `vsnip` users.
              -- require('luasnip').lsp_expand(args.body) -- For `luasnip` users.
              -- require('snippy').expand_snippet(args.body) -- For `snippy` users.
              -- vim.fn["UltiSnips#Anon"](args.body) -- For `ultisnips` users.
            end,
          },
          window = {
            -- completion = cmp.config.window.bordered(),
            -- documentation = cmp.config.window.bordered(),
          },
          mapping = cmp.mapping.preset.insert({
            ['<C-b>'] = cmp.mapping.scroll_docs(-4),
            ['<C-f>'] = cmp.mapping.scroll_docs(4),
            ['<C-Space>'] = cmp.mapping.complete(),
            ['<C-e>'] = cmp.mapping.abort(),
            ['<CR>'] = cmp.mapping.confirm({ select = true }), -- Accept currently selected item. Set `select` to `false` to only confirm explicitly selected items.
          }),
          sources = cmp.config.sources({
            { name = 'nvim_lsp' },
            -- { name = 'vsnip' }, -- For vsnip users.
            -- { name = 'luasnip' }, -- For luasnip users.
            { name = 'ultisnips' }, -- For ultisnips users.
            -- { name = 'snippy' }, -- For snippy users.
          }, {
            { name = 'buffer' },
          })
        })

        -- Set configuration for specific filetype.
        cmp.setup.filetype('gitcommit', {
          sources = cmp.config.sources({
            { name = 'cmp_git' }, -- You can specify the `cmp_git` source if you were installed it.
          }, {
            { name = 'buffer' },
          })
        })

        -- Use buffer source for `/` (if you enabled `native_menu`, this won't work anymore).
        cmp.setup.cmdline('/', {
          mapping = cmp.mapping.preset.cmdline(),
          sources = {
            { name = 'buffer' }
          }
        })

        -- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
        cmp.setup.cmdline(':', {
          mapping = cmp.mapping.preset.cmdline(),
          sources = cmp.config.sources({
            { name = 'path' }
          }, {
            { name = 'cmdline' }
          })
        })

        -- Setup lspconfig.
        local capabilities = require('cmp_nvim_lsp').update_capabilities(vim.lsp.protocol.make_client_capabilities())
      end
    }