code: func GetAndroidNotification(req PushNotification) *fcm.Message {
  	notification := &fcm.Message{
  		To:                    req.To,
  		Condition:             req.Condition,
  		CollapseKey:           req.CollapseKey,
  		ContentAvailable:      req.ContentAvailable,
  		MutableContent:        req.MutableContent,
  		DelayWhileIdle:        req.DelayWhileIdle,
  		TimeToLive:            req.TimeToLive,
  		RestrictedPackageName: req.RestrictedPackageName,
  		DryRun:                req.DryRun,
  	}
  
  	if len(req.Tokens) > 0 {
  		notification.RegistrationIDs = req.Tokens
  	}
  
  	if len(req.Priority) > 0 && req.Priority == "high" {
  		notification.Priority = "high"
  	}
  
  	// Add another field
  	if len(req.Data) > 0 {
  		notification.Data = make(map[string]interface{})
  		for k, v := range req.Data {
  			notification.Data[k] = v
  		}
  	}
  
  	notification.Notification = &req.Notification
  
  	// Set request message if body is empty
  	if len(req.Message) > 0 {
  		notification.Notification.Body = req.Message
  	}
  
  	if len(req.Title) > 0 {
  		notification.Notification.Title = req.Title
  	}
  
  	if v, ok := req.Sound.(string); ok && len(v) > 0 {
  		notification.Notification.Sound = v
  	}
  
  	return notification
  }
docs: // GetAndroidNotification use for define Android notification.
  // HTTP Connection Server Reference for Android
  // https://firebase.google.com/docs/cloud-messaging/http-server-ref