admin: fix static routing

admin/static.go

@@ -2,8 +2,17 @@ package main
 
 import (
 	"net/http"
+	"path"
 )
 
-func StaticRouting(w http.ResponseWriter, r *http.Request) {
-	http.ServeFile(w, r, "./static/index.html")
+type staticRouting struct{
+	StaticDir string
+}
+
+func StaticHandler(staticDir string) http.Handler {
+	return staticRouting{staticDir}
+}
+
+func (a staticRouting) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	http.ServeFile(w, r, path.Join(a.StaticDir, "index.html"))
 }