Create webserver structure in main thread.

Avoids a race.

webserver.go

@@ -41,7 +41,6 @@ func webserver() {
 	http.HandleFunc("/public-groups.json", publicHandler)
 	http.HandleFunc("/stats", statsHandler)
 
-	go func() {
 	server = &http.Server{
 		Addr:              httpAddr,
 		ReadHeaderTimeout: 60 * time.Second,
@@ -54,6 +53,7 @@ func webserver() {
 			go g.shutdown("server is shutting down")
 		}
 	})
+	go func() {
 		var err error
 		err = server.ListenAndServeTLS(
 			filepath.Join(dataDir, "cert.pem"),