Create internal/errorpage package

deploy_page.go

 package main
 
 import (
+	"./internal/helper"
 	"io/ioutil"
 	"net/http"
 	"path/filepath"
@@ -15,7 +16,7 @@ func handleDeployPage(documentRoot *string, handler http.Handler) http.HandlerFu
 			return
 		}
 
-		setNoCacheHeaders(w.Header())
+		helper.SetNoCacheHeaders(w.Header())
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
 		w.WriteHeader(http.StatusOK)
 		w.Write(data)

error_pages_test.go

 package main
 
 import (
+	"./internal/errorpage"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -25,7 +26,7 @@ func TestIfErrorPageIsPresented(t *testing.T) {
 		w.WriteHeader(404)
 		fmt.Fprint(w, "Not Found")
 	})
-	handleRailsError(&dir, h)(w, nil)
+	errorpage.Inject(dir, h)(w, nil)
 	w.Flush()
 
 	assertResponseCode(t, w, 404)
@@ -45,7 +46,7 @@ func TestIfErrorPassedIfNoErrorPageIsFound(t *testing.T) {
 		w.WriteHeader(404)
 		fmt.Fprint(w, errorResponse)
 	})
-	handleRailsError(&dir, h)(w, nil)
+	errorpage.Inject(dir, h)(w, nil)
 	w.Flush()
 
 	assertResponseCode(t, w, 404)

helpers.go

@@ -54,12 +54,6 @@ func cleanUpProcessGroup(cmd *exec.Cmd) {
 	cmd.Wait()
 }
 
-func setNoCacheHeaders(header http.Header) {
-	header.Set("Cache-Control", "no-cache, no-store, max-age=0, must-revalidate")
-	header.Set("Pragma", "no-cache")
-	header.Set("Expires", "Fri, 01 Jan 1990 00:00:00 GMT")
-}
-
 // Borrowed from: net/http/server.go
 // Return the canonical path for p, eliminating . and .. elements.
 func cleanURIPath(p string) string {

error_pages.go → internal/errorpage/error_pages.go

-package main
+package errorpage
 
 import (
+"../helper"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -12,7 +13,7 @@ type errorPageResponseWriter struct {
 	rw       http.ResponseWriter
 	status   int
 	hijacked bool
-	path     *string
+	path     string
 }
 
 func (s *errorPageResponseWriter) Header() http.Header {
@@ -37,14 +38,14 @@ func (s *errorPageResponseWriter) WriteHeader(status int) {
 	s.status = status
 
 	if 400 <= s.status && s.status <= 599 {
-		errorPageFile := filepath.Join(*s.path, fmt.Sprintf("%d.html", s.status))
+		errorPageFile := filepath.Join(s.path, fmt.Sprintf("%d.html", s.status))
 
 		// check if custom error page exists, serve this page instead
 		if data, err := ioutil.ReadFile(errorPageFile); err == nil {
 			s.hijacked = true
 
 			log.Printf("ErrorPage: serving predefined error page: %d", s.status)
-			setNoCacheHeaders(s.rw.Header())
+			helper.SetNoCacheHeaders(s.rw.Header())
 			s.rw.Header().Set("Content-Type", "text/html; charset=utf-8")
 			s.rw.WriteHeader(s.status)
 			s.rw.Write(data)
@@ -59,7 +60,7 @@ func (s *errorPageResponseWriter) Flush() {
 	s.WriteHeader(http.StatusOK)
 }
 
-func handleRailsError(documentRoot *string, handler http.Handler) http.HandlerFunc {
+func Inject(documentRoot string, handler http.Handler) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		rw := errorPageResponseWriter{
 			rw:   w,

internal/helper/helpers.go

@@ -16,6 +16,12 @@ func LogError(err error) {
 	log.Printf("error: %v", err)
 }
 
+func SetNoCacheHeaders(header http.Header) {
+	header.Set("Cache-Control", "no-cache, no-store, max-age=0, must-revalidate")
+	header.Set("Pragma", "no-cache")
+	header.Set("Expires", "Fri, 01 Jan 1990 00:00:00 GMT")
+}
+
 func OpenFile(path string) (file *os.File, fi os.FileInfo, err error) {
 	file, err = os.Open(path)
 	if err != nil {

main.go

@@ -14,6 +14,7 @@ In this file we start the web server and hand off to the upstream type.
 package main
 
 import (
+	"./internal/errorpage"
 	"flag"
 	"fmt"
 	"log"
@@ -95,7 +96,7 @@ func compileRoutes(u *upstream) {
 			u.handleServeFile(documentRoot, CacheExpireMax,
 				handleDevelopmentMode(developmentMode,
 					handleDeployPage(documentRoot,
-						handleRailsError(documentRoot,
+						errorpage.Inject(*documentRoot,
 							proxy,
 						),
 					),
@@ -107,7 +108,7 @@ func compileRoutes(u *upstream) {
 		httpRoute{"", nil,
 			u.handleServeFile(documentRoot, CacheDisabled,
 				handleDeployPage(documentRoot,
-					handleRailsError(documentRoot,
+					errorpage.Inject(*documentRoot,
 						proxy,
 					),
 				),