make it universal

config.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"golang.org/x/oauth2"
+)
+
+func readConfig(filePath string) (*oauth2.Token, error) {
+	if _, err := os.Stat(filePath); os.IsNotExist(err) {
+		f, err := os.Create(filePath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create config file: %v", err)
+		}
+		if _, err := f.Write([]byte("{}")); err != nil {
+			return nil, fmt.Errorf("failed to write empty object: %v", err)
+		}
+		return &oauth2.Token{}, nil
+	}
+
+	f, err := os.OpenFile(filePath, os.O_RDWR, 0644)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open config file: %v", err)
+	}
+	defer f.Close()
+
+	token := new(oauth2.Token)
+	if err := json.NewDecoder(f).Decode(token); err != nil {
+		return nil, fmt.Errorf("failed to decode json from config file: %v", err)
+	}
+
+	return token, nil
+}
+
+func writeConfig(filePath string, token *oauth2.Token) error {
+	f, err := os.OpenFile(filePath, os.O_WRONLY, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open config file: %v", err)
+	}
+	defer f.Close()
+
+	if err := json.NewEncoder(f).Encode(token); err != nil {
+		return fmt.Errorf("failed to encode json to config file: %v", err)
+	}
+
+	return nil
+}