nvim/after/plugin/lsp.lua

local keymap = vim.keymap.set

require('mason').setup({
    ui = {
        icons = {
            server = " ",
            lsp = " ",
            linter = " ",
            formatter = " ",

            package_installed = "✓",
            package_pending = "➜",
            package_uninstalled = "✗"
        },
    },
})

require("mason-lspconfig").setup({
    automatic_installation = true,
})

local lsp = require('lspconfig')

local cmp = require('cmp')
local cmp_select = {behavior = cmp.SelectBehavior.Select}

local opts = { noremap=true, silent=true }
--keymap('i', '<C-Space>', vim.diagnostic.open_float, opts)
--keymap('i', '<C-p>', vim.diagnostic.goto_prev, opts)
--keymap('i', '<C-n>', vim.diagnostic.goto_next, opts)
--keymap('i', '<C-Space>', cmp.mapping.complete(), opts)
--keymap('i', '<CR>', vim.diagnostic.setloclist, opts)
keymap('n', '<C-Space>', vim.diagnostic.open_float, opts)
keymap('n', '<C-p>', vim.diagnostic.goto_prev, opts)
keymap('n', '<C-n>', vim.diagnostic.goto_next, opts)
--keymap('i', '<C-Space>', cmp.mapping.complete(), opts)
keymap('n', '<CR>', vim.diagnostic.setloclist, opts)

cmp.setup({
    snippet = {
        expand = function(args)
            require('luasnip').lsp_expand(args.body)
        end,
    },
    mapping = {
        ['<C-p>'] = cmp.mapping.select_prev_item(cmp_select),
        ['<C-n>'] = cmp.mapping.select_next_item(cmp_select),
        ['<C-Space>'] = cmp.mapping.complete(cmp_select),
        ['<C-e>'] = cmp.mapping.close(),
        ['<CR>'] = cmp.mapping.confirm({
            behavior = cmp.ConfirmBehavior.Replace,
            select = true,
        }),
    },
    sources = {
        { name = 'nvim_lsp' },
        { name = 'luasnip' },
        { name = 'buffer' },
    },
})

vim.diagnostic.config({
    virtual_text = true,
})

local on_attach = function(client, bufnr)
    local function buf_set_keymap(...)
		vim.api.nvim_buf_set_keymap(bufnr, ...)
	end

	-- Mappings.
	local opts = { noremap = true, silent = true, buffer = bufnr}

	-- See `:help vim.lsp.*` for documentation on any of the below functions
	vim.keymap.set("n", "gd", "<cmd>Telescope lsp_definitions<CR>", opts)
	vim.keymap.set("n", "gr", "<cmd>Telescope lsp_references<CR>", opts)

	vim.keymap.set("n", "<C-j>", "<cmd>Telescope lsp_document_symbols<CR>", opts)
	vim.keymap.set("n", "<C-k>", "<cmd>lua vim.lsp.buf.signature_help()<CR>", opts)

	vim.keymap.set("n", "gi", "<cmd>Telescope lsp_implementations<CR>", opts)
	vim.keymap.set("n", "K", "<cmd>lua vim.lsp.buf.hover()<CR>", opts)
	vim.keymap.set("n", "<leader>D", "<cmd>Telescope lsp_type_definitions<CR>", opts)
	vim.keymap.set("n", "<leader>rn", "<cmd>lua vim.lsp.buf.rename()<CR>", opts)
	vim.keymap.set("n", "<leader>ca", "<cmd>Telescope lsp_code_actions<CR>", opts)
	vim.keymap.set("n", "gt", vim.lsp.buf.type_definition, {buffer=0})
	vim.keymap.set("n", "gi", vim.lsp.buf.implementation, {buffer=0})
	vim.keymap.set("n", "<leader>dj", vim.diagnostic.goto_next, {buffer=0})
	vim.keymap.set("n", "<leader>dk", vim.diagnostic.goto_prev, {buffer=0})
	vim.keymap.set("n", "<leader>dl", "<cmd>Telescope diagnostics<cr>", {buffer=0})
	vim.keymap.set("n", "<leader>r", vim.lsp.buf.rename, {buffer=0})
	vim.keymap.set("n", "<leader>ca", vim.lsp.buf.code_action, {buffer=0})

    -- Set autocommands conditional on server_capabilities
	if client.server_capabilities.document_highlight then
		vim.cmd([[
			augroup lsp_document_highlight
				autocmd! * <buffer>
				autocmd CursorHold <buffer> lua vim.lsp.buf.document_highlight()
				autocmd CursorMoved <buffer> lua vim.lsp.buf.clear_references()
			augroup END
		]])
	end
end

lsp.gopls.setup({
    on_attach = on_attach,
    flags = lsp_flags,
    settings = {
        gopls = {
            analyses = {
                unusedparams = true,
            },
            staticcheck = true,
        },
    },
})

lsp['lua_ls'].setup{
    on_attach = on_attach,
    flags = lsp_flags,
}

lsp['rust_analyzer'].setup{
    on_attach = on_attach,
    flags = lsp_flags,
    cmd = {
        "rustup", "run", "stable", "rust-analyzer",
    }
}

lsp.tsserver.setup{
    on_attach = on_attach,
    flags = lsp_flags,
}