do not clear lists when jumping to definitions (and enable async for Neovim)

autoload/go/def.vim

@@ -42,10 +42,11 @@ function! go#def#Jump(mode) abort
 
     call extend(cmd, ["definition", fname . ':#' . go#util#OffsetCursor()])
 
-    if go#util#has_job()
+    if go#util#has_job() || has('nvim')
       let l:spawn_args = {
             \ 'cmd': cmd,
             \ 'complete': function('s:jump_to_declaration_cb', [a:mode, bin_name]),
+            \ 'for': '_',
             \ }
 
       if &modified

autoload/go/def_test.vim

@@ -34,4 +34,33 @@ func! Test_jump_to_declaration_godef() abort
   endtry
 endfunc
 
+func! Test_Jump_leaves_lists() abort
+  try
+    let filename = 'def/jump.go'
+    let l:tmp = gotest#load_fixture(l:filename)
+
+    let expected = [{'lnum': 10, 'bufnr': bufnr('%'), 'col': 1, 'valid': 1, 'vcol': 0, 'nr': -1, 'type': '', 'pattern': '', 'text': 'quux'}]
+
+    call setloclist(winnr(), copy(expected), 'r' )
+    call setqflist(copy(expected), 'r' )
+
+    let l:bufnr = bufnr('%')
+    call cursor(6, 3)
+    call go#def#Jump('')
+
+    let start = reltime()
+    while bufnr('%') == l:bufnr && reltimefloat(reltime(start)) < 10
+      sleep 100m
+    endwhile
+
+    let actual = getloclist(winnr())
+    call gotest#assert_quickfix(actual, expected)
+
+    let actual = getqflist()
+    call gotest#assert_quickfix(actual, expected)
+  finally
+    call delete(l:tmp, 'rf')
+  endtry
+endfunc
+
 " vim: sw=2 ts=2 et

autoload/go/job.vim

@@ -22,6 +22,7 @@ endfunction
 "     See statusline.vim.
 "   'for':
 "     The g:go_list_type_command key to use to get the error list type to use.
+"     Errors will not be handled when the value is '_'.
 "     Defaults to '_job'
 "   'errorformat':
 "     The errorformat string to use when parsing errors. Defaults to
@@ -184,6 +185,10 @@ function! go#job#Options(args)
   let cbs.close_cb = function('s:close_cb', [], state)
 
   function state.show_errors(job, exit_status, data)
+    if self.for == '_'
+      return
+    endif
+
     let l:winid = win_getid(winnr())
     " Always set the active window to the window that was active when the job
     " was started. Among other things, this makes sure that the correct
@@ -225,6 +230,8 @@ function! go#job#Options(args)
       return
     endif
 
+    " only open the error window if user was still in the window from which
+    " the job was started.
     if self.winid == l:winid
       call go#list#Window(l:listtype, len(errors))
       if !self.bang