add Cache304 as an alternative to the server-side kataras/iris/cache middleware - it can perform better with less server overheat but it comes with a cost of 304 instead of 200 so custom clients must make that check

Former-commit-id: b0ba68c528c870fe060e2825c35689771a1d3680

cache/cache.go

@@ -1,4 +1,7 @@
-/* Package cache provides cache capabilities with rich support of options and rules.
+/* Package cache provides server-side caching capabilities with rich support of options and rules.
+
+Use it for server-side caching, see the `iris#Cache304` for an alternative approach that
+may fit your needs most.
 
 Example code:
 
@@ -37,6 +40,9 @@ import (
 //
 // All types of response can be cached, templates, json, text, anything.
 //
+// Use it for server-side caching, see the `iris#Cache304` for an alternative approach that
+// may fit your needs most.
+//
 // You can add validators with this function.
 func Cache(expiration time.Duration) *client.Handler {
 	return client.NewHandler(expiration)
@@ -49,6 +55,9 @@ func Cache(expiration time.Duration) *client.Handler {
 //
 // All types of response can be cached, templates, json, text, anything.
 //
+// Use it for server-side caching, see the `iris#Cache304` for an alternative approach that
+// may fit your needs most.
+//
 // it returns a context.Handler which can be used as a middleware, for more options use the `Cache`.
 //
 // Examples can be found at: https://github.com/kataras/iris/tree/master/_examples/#caching

cache/client/handler.go

@@ -163,7 +163,7 @@ func (h *Handler) ServeHTTP(ctx context.Context) {
 
 	// if it's valid then just write the cached results
 	entry.CopyHeaders(ctx.ResponseWriter().Header(), response.Headers())
-	context.SetLastModified(ctx, e.LastModified)
+	ctx.SetLastModified(e.LastModified)
 	ctx.StatusCode(response.StatusCode())
 	ctx.Write(response.Body())