Remove unnessary early header write

api/api.go

@@ -12,7 +12,7 @@ import (
 // always returns a router for the newest version of our API. We
 // use gorilla/mux because it is more convenient than net/http, e.g.
 // when extracting path parameters.
-func NewRouter() *mux.Router {
+func NewRouter() http.Handler {
 	router := mux.NewRouter()
 	// this can later be restricted to a specific host with
 	// `router.Host(...)` and to HTTPS with `router.Schemes("https")`