Fix a command in the vimrc

Author: hogedigo

vimrc

@@ -166,7 +166,7 @@ augroup END
 function! s:build_go_files()
   let l:file = expand('%')
   if l:file =~# '^\f\+_test\.go$'
-    call go#cmd#Test(0, 1)
+    call go#test#Test(0, 1)
   elseif l:file =~# '^\f\+\.go$'
     call go#cmd#Build(0)
   endif