*: enable nogo (go linter)

Also fix a bunch of small issues in our codebase, whoops.

This is ran automatically on `bazel build`.

Change-Id: If49ba956b4e2380344a765c30cd84ab760fc4c68
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1849
Reviewed-by: palid <palid@hackerspace.pl>
diff --git a/BUILD b/BUILD
index cbc4789..cb7fbf2 100644
--- a/BUILD
+++ b/BUILD
@@ -33,3 +33,11 @@
 buildifier(
     name = "buildifier",
 )
+
+load("@io_bazel_rules_go//go:def.bzl", "nogo")
+
+nogo(
+    name = "nogo",
+    vet = True,
+    visibility = ["//visibility:public"], # must have public visibility
+)