CookieJar在哪里保留cookie?

The CookieJar seems to persist cookies somewhere not in memory but I couldn't find these details on documentation. So where CookieJar persists cookies? Is there a way to change where the cookies are persisted?

PS: Reason for the question is that cookies seems to survive after program is restarted.

Package cookiejar

import "net/http/cookiejar" 

Package cookiejar implements an in-memory RFC 6265-compliant http.CookieJar.

jar.go

The implementation from net/http/cookiejar stores cookies in memory.

If you want a more persistent form of storage, you can do so by providing your own implementation of the http.CookieJar interface.