Change finalizer for closing HTTP connections to a class method.

See https://www.mikeperham.com/2010/02/24/the-trouble-with-ruby-finalizers/

Author: gkellogg

lib/sparql/client.rb

@@ -102,7 +102,7 @@ def initialize(url, **options, &block)
         @http = http_klass(@url.scheme)
 
         # Close the http connection when object is deallocated
-        ObjectSpace.define_finalizer(self, proc {@http.shutdown if @http.respond_to?(:shutdown)})
+        ObjectSpace.define_finalizer(self, self.class.finalize(@http))
       end
 
       if block_given?
@@ -113,6 +113,13 @@ def initialize(url, **options, &block)
       end
     end
 
+    # Close the http connection when object is deallocated
+    def self.finalize(klass)
+      proc do
+        klass.shutdown if klass.respond_to?(:shutdown)
+      end
+    end
+
     ##
     # Closes a client instance by finishing the connection.
     # The client is unavailable for any further data operations; an IOError is raised if such an attempt is made. I/O streams are automatically closed when they are claimed by the garbage collector.