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Dockerfile
main

.gitignore

main
go-http-proxy

README.md

Minimal Docker Image with Go HTTP Proxy

Dockerfile

FROM golang:stretch AS build
WORKDIR /build
RUN apt-get update && \
    apt-get install -y xz-utils
ADD https://github.com/upx/upx/releases/download/v3.95/upx-3.95-amd64_linux.tar.xz /usr/local
RUN xz -d -c /usr/local/upx-3.95-amd64_linux.tar.xz | \
    tar -xOf - upx-3.95-amd64_linux/upx > /bin/upx && \
    chmod a+x /bin/upx
COPY . .
RUN GO111MODULE=off CGO_ENABLED=0 GOOS=linux \
    go build  -a -tags netgo -ldflags '-w -s'  main.go && \
    upx main

FROM scratch
COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
COPY --from=build /build/main /main
WORKDIR /
CMD ["/main"]

main.go

package main

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

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		url := r.FormValue("url")
		if url == "" {
			w.WriteHeader(http.StatusBadRequest)
			w.Write([]byte("\"url\" param is required"))
			return
		}
		resp, err := http.Get(url)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			w.Write([]byte(fmt.Sprintf("Error fetching url [%s]: %s", url, err.Error())))
			return
		}
		// stream the resp body to our HTTP response, w
		writtenCount, err := io.Copy(w, resp.Body)
		if err != nil || writtenCount == 0 {
			w.WriteHeader(http.StatusInternalServerError)
			w.Write([]byte("Response was empty from url  " + url))
			return
		}
	})
	if port := os.Getenv("PORT"); port != "" {
		http.ListenAndServe(":"+port, nil)
	} else {
		log.Panic("PORT not set")
	}
}