Correct Entrypoint Redirect with Stripped or Added Path

middlewares/addPrefix.go

@@ -1,6 +1,7 @@
 package middlewares
 
 import (
+	"context"
 	"net/http"
 )
 
@@ -10,12 +11,21 @@ type AddPrefix struct {
 	Prefix  string
 }
 
+type key string
+
+const (
+	// AddPrefixKey is the key within the request context used to
+	// store the added prefix
+	AddPrefixKey key = "AddPrefix"
+)
+
 func (s *AddPrefix) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	r.URL.Path = s.Prefix + r.URL.Path
 	if r.URL.RawPath != "" {
 		r.URL.RawPath = s.Prefix + r.URL.RawPath
 	}
 	r.RequestURI = r.URL.RequestURI()
+	r = r.WithContext(context.WithValue(r.Context(), AddPrefixKey, s.Prefix))
 	s.Handler.ServeHTTP(w, r)
 }