Add Go package registry (#24687)

Fixes #7608

This PR adds a Go package registry usable with the Go proxy protocol.

![grafik](https://github.com/go-gitea/gitea/assets/1666336/328feb5c-3df2-4f9d-8eae-fe3126d14c37)

routers/api/packages/api.go

@@ -24,6 +24,7 @@ import (
 	"code.gitea.io/gitea/routers/api/packages/container"
 	"code.gitea.io/gitea/routers/api/packages/debian"
 	"code.gitea.io/gitea/routers/api/packages/generic"
+	"code.gitea.io/gitea/routers/api/packages/goproxy"
 	"code.gitea.io/gitea/routers/api/packages/helm"
 	"code.gitea.io/gitea/routers/api/packages/maven"
 	"code.gitea.io/gitea/routers/api/packages/npm"
@@ -312,6 +313,64 @@ func CommonRoutes(ctx gocontext.Context) *web.Route {
 				}, reqPackageAccess(perm.AccessModeWrite))
 			})
 		}, reqPackageAccess(perm.AccessModeRead))
+		r.Group("/go", func() {
+			r.Put("/upload", reqPackageAccess(perm.AccessModeWrite), goproxy.UploadPackage)
+			r.Get("/sumdb/sum.golang.org/supported", func(ctx *context.Context) {
+				ctx.Status(http.StatusNotFound)
+			})
+
+			// Manual mapping of routes because the package name contains slashes which chi does not support
+			// https://go.dev/ref/mod#goproxy-protocol
+			r.Get("/*", func(ctx *context.Context) {
+				path := ctx.Params("*")
+
+				if strings.HasSuffix(path, "/@latest") {
+					ctx.SetParams("name", path[:len(path)-len("/@latest")])
+					ctx.SetParams("version", "latest")
+
+					goproxy.PackageVersionMetadata(ctx)
+					return
+				}
+
+				parts := strings.SplitN(path, "/@v/", 2)
+				if len(parts) != 2 {
+					ctx.Status(http.StatusNotFound)
+					return
+				}
+
+				ctx.SetParams("name", parts[0])
+
+				// <package/name>/@v/list
+				if parts[1] == "list" {
+					goproxy.EnumeratePackageVersions(ctx)
+					return
+				}
+
+				// <package/name>/@v/<version>.zip
+				if strings.HasSuffix(parts[1], ".zip") {
+					ctx.SetParams("version", parts[1][:len(parts[1])-len(".zip")])
+
+					goproxy.DownloadPackageFile(ctx)
+					return
+				}
+				// <package/name>/@v/<version>.info
+				if strings.HasSuffix(parts[1], ".info") {
+					ctx.SetParams("version", parts[1][:len(parts[1])-len(".info")])
+
+					goproxy.PackageVersionMetadata(ctx)
+					return
+				}
+				// <package/name>/@v/<version>.mod
+				if strings.HasSuffix(parts[1], ".mod") {
+					ctx.SetParams("version", parts[1][:len(parts[1])-len(".mod")])
+
+					goproxy.PackageVersionGoModContent(ctx)
+					return
+				}
+
+				ctx.Status(http.StatusNotFound)
+			})
+		}, reqPackageAccess(perm.AccessModeRead))
 		r.Group("/generic", func() {
 			r.Group("/{packagename}/{packageversion}", func() {
 				r.Delete("", reqPackageAccess(perm.AccessModeWrite), generic.DeletePackage)