Dockerfile

FROM golang:1.12.3-stretch

ADD . /app
WORKDIR /app

RUN go build -o cloud-run-header-limit-demo .
RUN cp cloud-run-header-limit-demo /usr/local/bin/

CMD ["/usr/local/bin/cloud-run-header-limit-demo"]

main.go

package main

import (
	"fmt"
	"net/http"
	"os"
)

func handleIndex(resWriter http.ResponseWriter, req *http.Request) {
	longString := ""
	for i := 0; i < 10000; i++ {
		longString += "-"
	}

	// Set a very large header
	resWriter.Header().Set("X-Very-Large-Header", longString)

	fmt.Fprint(resWriter, "OK")
}

func main() {
	http.HandleFunc("/", handleIndex)

	var port = os.Getenv("PORT")
	if len(port) == 0 {
		port = "4565"
	}

	err := http.ListenAndServe(":"+port, nil)
	if err != nil {
		fmt.Println("Error listening on port", err)
	}
}