502 error code

TL;DR: If server directly closes the connection, client will get nothing EOF error. Than proxies convert it to 502 Bad Gateway error and mostly related with server side code.

There is good article about it https://blog.cloudflare.com/the-complete-guide-to-golang-net-http-timeouts/

In http server there is settings read and write timeouts. Write timeout is between you get the request body and reponse.

// not recommended in production codes
http.Server{
    ReadTimeout:  10 * time.Second,
    WriteTimeout: 10 * time.Second,
}

When we add timeout in the http-server code than it is working worse than without timeout. If our request takes 30 seconds than, we will wait 30 seconds and after that we will get EOF error.

Best of do this kind of things outside of the microservice.