use SSHFS to mount Synology NAS

Just enable the SFTP Service in Control Panel->File Services.

Then mount with sshfs username@machine:/homes/username /directory

To add to the answer from @vindolin (..I don't have enough reputation just to add a comment),

As well as enabling SFTP, you also need to enable permissions to FTP for the specified user. If that permission isn't enabled, you will continue to get the connection reset by peer error.