How can i send cookie in figma plugin

Recently, I develop a figma plugin to use with my system and service. I need request api of back-end which requires cookie that stores in figma. But when I try set “Cookie” in header of a request, I get error that chromium dose not allow javascript to do it. So now I have no idea to send cookie to back-end, what can I do? I do not want to change my back-end suck as jwt for auth.