Document gofmt-command

Fix #3065

[ci-skip]

layers/+lang/go/README.org

@@ -8,12 +8,13 @@
  - [[#install][Install]]
    - [[#pre-requisites][Pre-requisites]]
    - [[#layer][Layer]]
+ - [[#configuration][Configuration]]
+   - [[#formatting][Formatting]]
  - [[#working-with-go][Working with Go]]
    - [[#go-commands-start-with-m][Go commands (start with =m=):]]
    - [[#go-oracle][Go Oracle]]
 
 * Description
-
 This layer adds extensive support for go.
 
 ** Features:
@@ -24,7 +25,6 @@ This layer adds extensive support for go.
 * Install
 
 ** Pre-requisites
-
 You will need =gocode= and =godef=:
 
 #+BEGIN_SRC sh
@@ -36,13 +36,22 @@ You will need =gocode= and =godef=:
 Make sure that =gocode= executable is in your PATH.
 
 ** Layer
-
 To use this contribution add it to your =~/.spacemacs=
 
 #+BEGIN_SRC emacs-lisp
   (setq-default dotspacemacs-configuration-layers '(go))
 #+END_SRC
 
+* Configuration
+
+** Formatting
+By default, go buffers are run through =gofmt= on save. To use a different
+formatter, set the value of =gofmt-command=, e.g.
+
+#+begin_src emacs-lisp
+  (setq gofmt-command "goimports")
+#+end_src
+
 * Working with Go
 
 ** Go commands (start with =m=):