Test preservation of go retract directive

go_modules/spec/dependabot/go_modules/file_updater/go_mod_updater_spec.rb

@@ -103,6 +103,13 @@
           it { is_expected.to include("go 1.13") }
         end
 
+        context "when a retract directive is present" do
+          let(:project_name) { "go_retracted" }
+
+          it { is_expected.to include("// reason for retraction") }
+          it { is_expected.to include("retract v1.0.5") }
+        end
+
         describe "a dependency who's module path has changed (inc version)" do
           let(:project_name) { "module_path_and_version_changed" }
 

go_modules/spec/fixtures/projects/go_retracted/go.mod

@@ -0,0 +1,10 @@
+module github.com/dependabot/vgotest
+
+go 1.16
+
+require (
+	rsc.io/quote v1.4.0
+)
+
+// reason for retraction
+retract v1.0.5

go_modules/spec/fixtures/projects/go_retracted/main.go

@@ -0,0 +1,8 @@
+package main
+
+import (
+	_ "rsc.io/quote"
+)
+
+func main() {
+}