Session.opApply

//import vibe.http.server;
// workaround for cyclic module ctor compiler error
class HTTPServerRequest { Session session; }
class HTTPServerResponse { import vibe.core.stream; OutputStream bodyWriter() @safe { assert(false); } string contentType; }

// sends all session entries to the requesting browser
// assumes that all entries are strings
void handleRequest(scope HTTPServerRequest req, scope HTTPServerResponse res)
{
	res.contentType = "text/plain";
	req.session.opApply((key) @safe {
		res.bodyWriter.write(key ~ ": " ~ req.session.get!string(key) ~ "\n");
		return 0;
	});
}