NetworkSingleton.cs

// NetworkSingleton.cs
public class NetworkSingleton : MonoBehaviour {
  
  public static NetworkSingleton Instance;
  private string URL = "myfirebaseid.firebaseio.com";
  private string APIKEY = "firebasedatabaseKey"; 
  
  public Firebase firebase;
  
  private void Awake () {
                if( null != Instance ){
			Destroy( gameObject );
		}else{
			Instance = this;
		}
		firebase = Firebase.CreateNew (URL, APIKEY);
  }
}