using unique_lock instead of lock_guard

Author: Klaim

libmamba/src/core/package_fetcher.cpp

@@ -458,7 +458,7 @@ namespace mamba
     void PackageFetcher::update_urls_txt() const
     {
         // TODO: check if this lock is really required
-        std::lock_guard<std::mutex> lock(urls_txt_mutex);
+        std::unique_lock lock{ urls_txt_mutex };
         const auto urls_file_path = m_cache_path / "urls.txt";
         std::ofstream urls_txt(urls_file_path.std_path(), std::ios::app);
         urls_txt << url() << std::endl;

libmamba/src/core/package_handling.cpp

@@ -740,7 +740,7 @@ namespace mamba
     void extract(const fs::u8path& file, const fs::u8path& dest, const ExtractOptions& options)
     {
         static std::mutex extract_mutex;
-        std::lock_guard<std::mutex> lock(extract_mutex);
+        std::unique_lock lock{ extract_mutex };
 
         if (util::ends_with(file.string(), ".tar.bz2"))
         {