A small Go server that reflects request headers, useful for testing deployments.
A Docker image is available on Docker Hub.
docker pull aodin/blackmirror
docker run -p 8080:8080 aodin/blackmirror
It was built for multi-arch and tagged with:
docker buildx create --use --name multi || true
docker buildx inspect --bootstrap
VERSION=$(git describe --tags --always)
docker buildx build \
--platform linux/amd64,linux/arm64 \
--build-arg VERSION=$VERSION \
-t aodin/blackmirror:$VERSION \
-t aodin/blackmirror:latest \
--push .
The server can be built locally with go:
go build -mod=vendor .
The server will respond to a request for any method and path with the HTTP/1.1 wire format as a text/plain document.
Request:
GET localhost:8080/yo
Response:
GET /yo HTTP/1.1
Host: localhost:8080
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Connection: keep-alive
Priority: u=0, i
Sec-Fetch-Dest: document
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: none
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.6 Safari/605.1.15
It accepts PORT / HOST environment variables and -port / -host flags, with the flags taking precendence. Its default address is :8080.
PORT=8081 HOST=0.0.0.0 go run blackmirror.go -port=8082 -host="localhost"
Happy hacking!
aodin, 2025