Faster external package indexing for go-mode

go-find-external.el

(defun go-packages-find ()
  (sort
   (delete-dups
    (cl-mapcan (lambda (topdir)
                 (let ((pkgdir (concat topdir "/pkg")))
                   (mapcar (lambda (file)
                             (let ((sub (substring file 0 -2)))
                               (mapconcat #'identity (cdr (split-string sub "/")) "/")))
                           (split-string (shell-command-to-string
                                          (format "find \"%s\" -not -path \"%s/tool*\" -not -path \"%s/obj/*\" -name \"*.a\"  -printf \"%%P\\n\""
                                                  pkgdir pkgdir pkgdir))))))
               (go-root-and-paths)))
   #'string<))

(setq go-packages-function 'go-packages-find)