use gopls in rename command for go (#3412)

Vim-go uses the deprecated gorename command that doesn't support Go modules. The latest release go gopls support renaming and is the new way forward.

See: 
* golang/go#27571
* fatih/vim-go#2366

autoload/SpaceVim/layers/lang/go.vim

@@ -60,6 +60,7 @@ function! SpaceVim#layers#lang#go#config() abort
   let g:syntastic_mode_map = { 'mode': 'active', 'passive_filetypes': ['go'] }
   let g:neomake_go_gometalinter_args = ['--disable-all']
   let g:go_snippet_engine = 'neosnippet'
+  let g:go_rename_command = 'gopls'
 
   if SpaceVim#layers#lsp#check_filetype('go')
     call SpaceVim#mapping#gd#add('go',