Fixed go: go.mod file not found in current directory or any parent directory in spec

Author: sue445

_tools/ruby_h_to_go/spec/ruby_h_to_go/cli_spec.rb

@@ -13,6 +13,10 @@
   describe "#perform" do
     subject { cli.perform }
 
+    before do
+      FileUtils.cp(File.join(project_root_dir, "go.mod"), temp_dir)
+    end
+
     it { expect { subject }.not_to raise_error }
   end
 end

_tools/ruby_h_to_go/spec/spec_helper.rb

@@ -111,3 +111,8 @@
     meta[:aggregate_failures] = true
   end
 end
+
+# @return [String]
+def project_root_dir
+  File.expand_path("../../..", __dir__)
+end