Upgrade Request Required when running exec in Kubernetes
I found out that this has to do with http2, because Kubernetes exec uses SPDY, the problem went away when I upgraded to curl version > 7.36 and installed nghttp2 on the server.
After installing curl I was able to get the response by adding some headers
curl -H "Connection: upgrade" -H "Upgrade: SPDY/3.1" {master url:port/pod/exec}