For testing http2 on http(Cleartext), h2c not on https(on TLS), h2.
# docker build --rm -t knknkn1162/h2c_test .
# accept signal
docker run -it --rm --init -p 8080:1010 knknkn1162/h2c_test
# stop with Ctrl-C
# check with "-v"
# or "--trace /dev/stdout"
# or wireshark app.
curl http://localhost:8080 --http2
curl --http2-prior-knowledge http://localhost:1010