call mason in a safer way, and initalize servers better

after/plugin/lsp.lua

@@ -62,10 +62,25 @@ vim.lsp.handlers['textDocument/signatureHelp'] = vim.lsp.with(
   vim.lsp.handlers.signature_help, { border = 'shadow' })
 
 -- get servers and attach to them
-require('mason').setup {}
-require('mason-lspconfig').setup {}
-
-local get_servers = require('mason-lspconfig').get_installed_servers
-for _, server_name in ipairs(get_servers()) do
-  lspconfig[server_name].setup({ on_attach = lsp_attach, })
+local status_ok1, mason = pcall(require, "mason")
+if not status_ok1 then
+	return
 end
+mason.setup {}
+
+local status_ok2, masonlspconfig = pcall(require, "mason-lspconfig")
+if not status_ok2 then
+	return
+end
+masonlspconfig.setup {}
+masonlspconfig.setup_handlers {
+  function (server_name)
+    lspconfig[server_name].setup { on_attach = lsp_attach }
+  end,
+
+  -- specific servers can be setup as follows:
+  -- ["rust_analyzer"] = function ()
+  --   require("rust-tools").setup {}
+  -- end
+  -- check out :help mason-lspconfig for more info
+}