Implement simple forward proxy for HTTP

.gitignore

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+/go-proxy

go.mod

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+module go-proxy
+
+go 1.19

main.go

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+package main
+
+import (
+	"io"
+	"log"
+	"net/http"
+	"os"
+)
+
+func forward(w http.ResponseWriter, r *http.Request) {
+	resp, err := http.DefaultTransport.RoundTrip(r)
+	if err != nil {
+		log.Print(err)
+		http.Error(w, http.StatusText(http.StatusServiceUnavailable), http.StatusServiceUnavailable)
+		return
+	}
+	for header, values := range resp.Header {
+		for _, value := range values {
+			w.Header().Add(header, value)
+		}
+	}
+	w.WriteHeader(resp.StatusCode)
+	io.Copy(w, resp.Body)
+}
+
+func main() {
+	err := http.ListenAndServe(":8080", http.HandlerFunc(forward))
+	if err != nil {
+		log.Print(err)
+		os.Exit(1)
+	}
+}