cookie cannot work with domain "mysubsubdomain.mysubdomain.localhost.com"

[guangdashao]

in the sessions.go file ,the function updateCookie with sub code:

// RFC2109, we allow level 1 subdomains, but no further
			// if we have localhost.com , we want the localhost.cos.
			// so if we have something like: mysubdomain.localhost.com we want the localhost here
			// if we have mysubsubdomain.mysubdomain.localhost.com we want the .mysubdomain.localhost.com here
			// slow things here, especially the 'replace' but this is a good and understable( I hope) way to get the be able to set cookies from subdomains & domain with 1-level limit
			if dotIdx := strings.LastIndexByte(requestDomain, '.'); dotIdx > 0 {
				// is mysubdomain.localhost.com || mysubsubdomain.mysubdomain.localhost.com
				s := requestDomain[0:dotIdx] // set mysubdomain.localhost || mysubsubdomain.mysubdomain.localhost
				if secondDotIdx := strings.LastIndexByte(s, '.'); secondDotIdx > 0 {
					//is mysubdomain.localhost ||  mysubsubdomain.mysubdomain.localhost
					s = s[secondDotIdx+1:] // set to localhost || mysubdomain.localhost
				}
				// replace the s with the requestDomain before the domain's siffux
				subdomainSuff := strings.LastIndexByte(requestDomain, '.')
				if subdomainSuff > len(s) { // if it is actual exists as subdomain suffix
					requestDomain = strings.Replace(requestDomain, requestDomain[0:subdomainSuff], s, 1) // set to localhost.com || mysubdomain.localhost.com
				}
			}
			// finally set the .localhost.com (for(1-level) || .mysubdomain.localhost.com (for 2-level subdomain allow)
			cookie.Domain = "." + requestDomain // . to allow persistence

but , i found requestDomain with value "mysubsubdomain.mysubdomain.localhost.com" or "mysubdomain.localhost.com"， all come out "localhost.com" ，not as the note says 。