some major improvements to the (server-side) cache middleware and an example of a client-side responsibility cache

Former-commit-id: 93d3a7a6f163c6d49f315f86d10e63f7b1b1d93a

cache/entry/response.go

@@ -1,19 +1,21 @@
 package entry
 
+import "net/http"
+
 // Response is the cached response will be send to the clients
 // its fields setted at runtime on each of the non-cached executions
 // non-cached executions = first execution, and each time after
-// cache expiration datetime passed
+// cache expiration datetime passed.
 type Response struct {
-	// statusCode for the response cache handler
+	// statusCode for the response cache handler.
 	statusCode int
-	// contentType for the response cache handler
-	contentType string
-	// body is the contents will be served by the cache handler
+	// body is the contents will be served by the cache handler.
 	body []byte
+	// the total headers of the response, including content type.
+	headers http.Header
 }
 
-// StatusCode returns a valid status code
+// StatusCode returns a valid status code.
 func (r *Response) StatusCode() int {
 	if r.statusCode <= 0 {
 		r.statusCode = 200
@@ -22,14 +24,19 @@ func (r *Response) StatusCode() int {
 }
 
 // ContentType returns a valid content type
-func (r *Response) ContentType() string {
-	if r.contentType == "" {
-		r.contentType = "text/html; charset=utf-8"
-	}
-	return r.contentType
+// func (r *Response) ContentType() string {
+// 	if r.headers == "" {
+// 		r.contentType = "text/html; charset=utf-8"
+// 	}
+// 	return r.contentType
+// }
+
+// Headers returns the total headers of the cached response.
+func (r *Response) Headers() http.Header {
+	return r.headers
 }
 
-// Body returns contents will be served by the cache handler
+// Body returns contents will be served by the cache handler.
 func (r *Response) Body() []byte {
 	return r.body
 }