Exposing URLs for querying images

I want to return some chunk information through https://deqv7-6qaaa-aaaai-qfkna-cai.raw.ic0.app/ .
But as you see the Callback did not work.
It just return the first chunk.
So,how can i return information thurough Callback to return chunk information.
This my code http_demo/main.mo at main · xiaoyuanxun/http_demo · GitHub
Hope someone would help me
I will be very grateful.