go: make go-tab-width a regular layer variable

layers/+lang/go/README.org

@@ -11,6 +11,7 @@
  - [[#configuration][Configuration]]
    - [[#formatting][Formatting]]
    - [[#indentation][Indentation]]
+   - [[#tests][Tests]]
  - [[#working-with-go][Working with Go]]
    - [[#go-commands-start-with-m][Go commands (start with =m=):]]
    - [[#go-oracle][Go Oracle]]
@@ -62,19 +63,14 @@ or
 #+end_src
 
 ** Indentation
-By default, the width of tab in Go mode is 8 spaces. To use a different value
-for tab width, set the value of =go-tab-width=, e.g.
-
-#+begin_src emacs-lisp
-  (setq go-tab-width 4)
-#+end_src
-
-or
+By default, the tab widt in Go mode is 8 spaces. To use a different value
+set the layer variable =go-tab-width=, e.g.
 
 #+begin_src emacs-lisp
   (go :variables go-tab-width 4)
 #+end_src
 
+** Tests
 If you're using =gocheck= in your project you can use the
 =go-use-gocheck-for-testing= variable to enable suite testing and to get single
 function testing to work.

layers/+lang/go/config.el

@@ -15,3 +15,6 @@
 
 (defvar go-use-gocheck-for-testing nil
   "If using gocheck for testing when running the tests -check.f will be used instead of -run to specify the test that will be ran. Gocheck is mandatory for testing suites.")
+
+(defvar go-tab-width 8
+  "Set the `tab-width' in Go mode. Default is 8.")

layers/+lang/go/packages.el

@@ -9,11 +9,6 @@
         (go-rename :location local)
         ))
 
-(defcustom go-tab-width 8
-  "`tab-width' in Go mode. Default is 8."
-  :type 'integer
-  :group 'go)
-
 (defun go/post-init-flycheck ()
   (spacemacs/add-flycheck-hook 'go-mode))
 
@@ -23,12 +18,14 @@
       (unless (getenv var)
         (exec-path-from-shell-copy-env var))))
 
-  (add-hook 'go-mode-hook
-            (lambda ()
-              (setq-local tab-width go-tab-width)))
-
   (use-package go-mode
     :defer t
+    :init
+    (progn
+      (defun spacemacs//go-set-tab-width ()
+        "Set the tab width."
+        (setq-local tab-width go-tab-width))
+      (add-hook 'go-mode-hook 'spacemacs//go-set-tab-width))
     :config
     (progn
       (add-hook 'before-save-hook 'gofmt-before-save)