Only use show-trailing-whitespace in prog-mode

.emacs.d/init.el

@@ -14,7 +14,6 @@
       vc-follow-symlinks t
       custom-file (expand-file-name "~/.emacs.d/custom.el")
       gc-cons-threshold 100000000)
-(setq-default show-trailing-whitespace t)
 (load-theme 'fred t)
 (savehist-mode 1)
 (show-paren-mode 1)
@@ -194,6 +193,11 @@
   ; bind a key to revert buffers with no prompt
   (bind-key "C-x M-v" (lambda () (interactive) (revert-buffer t t t))))
 
+(use-package prog-mode
+  :config
+  (add-hook 'prog-mode-hook
+            #'(lambda () (setq-local show-trailing-whitespace t))))
+
 ;;;; external packages (required)
 (use-package company :ensure
   :config