Setting vim session name same as vim servername from vimrc -

basically i'm trying achieve set vim-session name same vim servername vimrc, i.e.

i'm using vim-session plugin , provides option set name of autosave session setting g:session_autosave_to in vimrc, i'm trying achieve let g:session_autosave_to=v:servername

don't know that's right way do, believe should have worked , session name should have been set servername, not seem happen.

any appreciated.