[#1239] addressed comments

src/lib/util/unlock_guard.h

@@ -0,0 +1,43 @@
+// Copyright (C) 2020 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef UNLOCK_GUARD_H
+#define UNLOCK_GUARD_H
+
+#include <boost/noncopyable.hpp>
+
+namespace isc {
+namespace util {
+
+/// @brief Unlock Guard.
+///
+/// Acts as a reverse std::lock_guard.
+template<typename Lock>
+class UnlockGuard : public boost::noncopyable {
+public:
+    /// @brief Constructor.
+    ///
+    /// Unlock mutex object on constructor.
+    explicit UnlockGuard(Lock& lock) : lock_(lock) {
+        lock_.unlock();
+    }
+
+    /// @brief Destructor.
+    ///
+    /// Lock mutex object on destructor.
+    ~UnlockGuard() {
+        lock_.lock();
+    }
+
+private:
+    /// @brief The mutex object.
+    Lock& lock_;
+};
+
+} // namespace util
+} // namespace isc
+
+#endif // UNLOCK_GUARD_H