Index: lib/net/imap.rb
===================================================================
--- lib/net/imap.rb	(revision 12813)
+++ lib/net/imap.rb	(working copy)
@@ -289,7 +289,7 @@
       else
         @sock.shutdown
       end
-      @receiver_thread.join
+      @receiver_thread.join(5).nil? && @receiver_thread.kill
       @sock.close
     end