support cors in rest server

rest/handlers.go

@@ -0,0 +1,29 @@
+package rest
+
+import (
+	"net/http"
+	"strings"
+)
+
+const (
+	allowOrigin  = "Access-Control-Allow-Origin"
+	allOrigin    = "*"
+	allowMethods = "Access-Control-Allow-Methods"
+	allowHeaders = "Access-Control-Allow-Headers"
+	headers      = "Content-Type, Content-Length, Origin"
+	methods      = "GET, HEAD, POST, PATCH, PUT, DELETE"
+	separator    = ", "
+)
+
+func CorsHandler(origins ...string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if len(origins) > 0 {
+			w.Header().Set(allowOrigin, strings.Join(origins, separator))
+		} else {
+			w.Header().Set(allowOrigin, allOrigin)
+		}
+		w.Header().Set(allowMethods, methods)
+		w.Header().Set(allowHeaders, headers)
+		w.WriteHeader(http.StatusNoContent)
+	})
+}