Add server skeleton with directory app and local dev loop

main.go

@@ -0,0 +1,23 @@
+// Heliosian serves the Helios school community apps.
+package main
+
+import (
+	"log"
+	"net/http"
+	"os"
+
+	"heliosian/internal/data"
+	"heliosian/internal/directory"
+)
+
+func main() {
+	mux := http.NewServeMux()
+	directory.Register(mux, data.Dir{Root: "sampledata"})
+	mux.Handle("GET /{$}", http.RedirectHandler("/directory/", http.StatusFound))
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "8080"
+	}
+	log.Printf("listening on http://localhost:%s", port)
+	log.Fatal(http.ListenAndServe(":"+port, mux))
+}