fix: docker healthcheck

Author: ilbertt

Dockerfile

@@ -25,11 +25,22 @@ RUN cargo build --release
 ### run the IC WS Gateway (we don't need the rust toolchain to run the binary)
 FROM debian:bullseye-slim AS runtime
 WORKDIR /ic-ws-gateway
+# install some utils
+RUN apt update
+RUN apt install -y curl
 # copy the compiled binary
 COPY --from=builder /ic-ws-gateway/target/release/ic_websocket_gateway .
 
 EXPOSE 8080
 EXPOSE 9000
 
+HEALTHCHECK --timeout=30s --interval=30s --retries=5 \
+  CMD curl -i -N \
+    -H "Connection: Upgrade" \
+    -H "Upgrade: websocket" \
+    -H "Sec-WebSocket-Version: 13" \
+    -H "Sec-WebSocket-Key: jWPXCaHslL1epUzz0k29Qw==" \
+    -X GET --head http://127.0.0.1:8080 | grep -q "HTTP/1.1 101 Switching Protocols" && exit 0 || exit 1
+
 # run the Gateway
 ENTRYPOINT ["/ic-ws-gateway/ic_websocket_gateway"]