Add golang formatting documentation

This patch is migrated from [0] as the repo used to store Airship
docs has changed to airship/docs.

This patch addresses feedback found in the other patch by removing
the manual import order specified to follow PEP8 standards as found
in the OpenStack docs in favor of using the goimports tool.

It is expected that when code is submitted it should have gofmt and
goimports run against it before hand - but these will be enforced
at the gate.

Change-Id: I624bade922e034205643a5214295a0febea7953b

doc/source/code-conventions.rst

@@ -106,9 +106,18 @@ readability and maintainability.
 Known Standards
 -------------------------------------------------------
 Language         Tools Used
-===============  ======================================
+===============  ======================================
+Go               gofmt
 Python           YAPF, Flake8
 ===============  ======================================
+
+Go Formatting
+~~~~~~~~~~~~~~~~~~~
+
+Go code should be formatted using gofmt. When using gofmt be sure to use the
+-s flag to include simplification of code for example::
+
+  gofmt -s /path/to/file.go
 
 Python PEP-8 Formatting
 ~~~~~~~~~~~~~~~~~~~~~~~