automatic support for go get on deep subpackages

main.go

@@ -342,6 +342,19 @@ func (this *Application) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			r.URL.Path = r.URL.Path[8:]
 			http.FileServer(http.Dir(`static`)).ServeHTTP(w, r)
 
+		} else if r.URL.Query().Get("go-get") == "1" {
+			// This wasn't one of our standard `/repo` paths, but there is the ?go-get=1 parameter
+			// It must be a subpackage request
+			// We can't serve the proper go-import meta tag immediately because
+			// we haven't looked up the go.mod yet. Just redirect to the root
+			// package - `go get` will follow redirects and the resulting meta tag is correct
+
+			slashParts := strings.SplitN(r.URL.Path, `/`, 3) // len === 3 is guaranteed from earlier if cases
+
+			w.Header().Set(`Location`, `/`+slashParts[1])
+			w.WriteHeader(301)
+			return
+
 		} else {
 			http.Error(w, "not found", 404)
 		}