Fix go get response if only app URL is custom in configuration (#2634)

* Fix go get response if only app URL is custom in configuration

* Rewrite to update Domain setting to match AppURL

Author: lafriks

modules/context/context.go

@@ -194,7 +194,7 @@ func Contexter() macaron.Handler {
 	</body>
 </html>
 `, map[string]string{
-				"GoGetImport":    path.Join(setting.Domain, setting.AppSubURL, ctx.Link),
+				"GoGetImport":    ComposeGoGetImport(ownerName, strings.TrimSuffix(repoName, ".git")),
 				"CloneLink":      models.ComposeHTTPSCloneURL(ownerName, repoName),
 				"GoDocDirectory": prefix + "{/dir}",
 				"GoDocFile":      prefix + "{/dir}/{file}#L{line}",

modules/setting/setting.go

@@ -10,6 +10,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io"
+	"net"
 	"net/mail"
 	"net/url"
 	"os"
@@ -664,6 +665,12 @@ func NewContext() {
 	// This value is empty if site does not have sub-url.
 	AppSubURL = strings.TrimSuffix(url.Path, "/")
 	AppSubURLDepth = strings.Count(AppSubURL, "/")
+	// Check if Domain differs from AppURL domain than update it to AppURL's domain
+	// TODO: Can be replaced with url.Hostname() when minimal GoLang version is 1.8
+	urlHostname := strings.SplitN(url.Host, ":", 2)[0]
+	if urlHostname != Domain && net.ParseIP(urlHostname) == nil {
+		Domain = urlHostname
+	}
 
 	var defaultLocalURL string
 	switch Protocol {