Set cache-control: no-cache to heath response

CHANGELOG.md

@@ -7,7 +7,8 @@
 ### Change
 - Change `IMGPROXY_FORMAT_QUALITY` default value to `avif=65`.
 - Change `IMGPROXY_AVIF_SPEED` default value to `8`.
-- Change `IMGPROXY_PREFERRED_FORMATS` default value to `jpeg,png,gif`;
+- Change `IMGPROXY_PREFERRED_FORMATS` default value to `jpeg,png,gif`.
+- Set `Cache-Control: no-cache` header to the health check responses.
 
 ## [3.11.0] - 2022-11-17
 ### Add

server.go

@@ -166,6 +166,7 @@ func withPanicHandler(h router.RouteHandler) router.RouteHandler {
 
 func handleHealth(reqID string, rw http.ResponseWriter, r *http.Request) {
 	router.LogResponse(reqID, r, 200, nil)
+	rw.Header().Set("Cache-Control", "no-cache")
 	rw.WriteHeader(200)
 	rw.Write(imgproxyIsRunningMsg)
 }