store references to IO objects to prevent "Bad file descriptor - (Errno::EBADF)"

lib/mysqlplus.rb

@@ -3,7 +3,7 @@ require 'mysql'
 class Mysql
   def async_query(sql)
     send_query(sql)
-    select([IO.new(socket)],nil,nil,nil)
+    select [ (@sockets ||= {})[socket] ||= IO.new(socket) ], nil, nil, nil
     get_result
   end
 end