Rewrite using async/await for synchronization instead of using lock statement using C#

public void Notify(object sender, StockNotification e)
{

lock (ToLock)
{
Console.WriteLine(brokerName.PadRight(11) + e.StockName.PadRight(11) + e.CurrentValue.ToString().PadRight(11) + e.Changes.ToString().PadRight(11));
}
lock (ToLock)
{
string directory = "/Users/Desktop/StockMarket";
string filename = "stocksreport.txt";
string path = directory + filename;

bool FileExists = File.Exists(path);

if (!File.Exists(path))
{
using (StreamWriter writer = File.CreateText(path))
{

writer.WriteLine("Date".PadRight(11) + "ttStock".PadRight(11) + "Initial".PadRight(11) + "Current".PadRight(11));
writer.WriteLine(e.Date.PadRight(11) + e.StockName.PadRight(11) + e.InitialValue.ToString().PadRight(11) + e.CurrentValue.ToString().PadRight(11));

writer.Flush();
}
}
else if (File.Exists(path))
{
using (StreamWriter writer = File.AppendText(path))
{
writer.WriteLine(e.Date.PadRight(11) + e.StockName.PadRight(11) + e.InitialValue.ToString().PadRight(11) + e.CurrentValue.ToString().PadRight(11));
writer.Flush();
}
}

}
}