Tiny debug image

Dockerfile

FROM golang:alpine as build
WORKDIR /usr/src/app
RUN apk --no-cache add upx
COPY ./server.go ./
ENV CGO_ENABLED=0
RUN go build -o server server.go
RUN upx --brute server

# ---

FROM scratch
COPY --from=build /usr/src/app/server ./server
ENTRYPOINT ["./server"]

server.go

package main

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

func respondOk(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintln(w, "OK")
}

func respondEnv(w http.ResponseWriter, r *http.Request) {
	for _, pair := range os.Environ() {
		fmt.Fprintln(w, pair)
	}
}

func respondName(w http.ResponseWriter, r *http.Request) {
	name := os.Getenv("NAME")

	if len(name) == 0 {
		fmt.Fprintln(w, "NONE")
	} else {
		fmt.Fprintln(w, name)
	}
}

func withLogging(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s %s\n", r.RemoteAddr, r.Method, r.URL)
		handler.ServeHTTP(w, r)
	})
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", respondOk)
	mux.HandleFunc("/env", respondEnv)
	mux.HandleFunc("/name", respondName)

	log.Println("Listening on port 8080...")
	log.Fatal(http.ListenAndServe(":8080", withLogging(mux)))
}