Load sheet into in-memory data model and serve it as the API

main.go

@@ -10,9 +10,29 @@ import (
 	"heliosian/internal/directory"
 )
 
+func directorySource() data.Source {
+	sheetID := os.Getenv("DIRECTORY_SHEET")
+	if sheetID == "" {
+		return data.Dir{Root: "sampledata"}
+	}
+	keyFile, err := data.KeyFile()
+	if err != nil {
+		log.Fatalf("[ERROR] %v", err)
+	}
+	source, err := data.NewSheet(keyFile, map[string]string{"directory": sheetID})
+	if err != nil {
+		log.Fatalf("[ERROR] load directory sheet: %v", err)
+	}
+	return source
+}
+
 func main() {
+	cache, err := directory.NewCache(directorySource())
+	if err != nil {
+		log.Fatalf("[ERROR] load directory data: %v", err)
+	}
 	mux := http.NewServeMux()
-	directory.Register(mux, data.Dir{Root: "sampledata"})
+	directory.Register(mux, cache)
 	mux.Handle("GET /{$}", http.RedirectHandler("/directory/", http.StatusFound))
 	port := os.Getenv("PORT")
 	if port == "" {