CosmosDriver.cs

public async Task<Customer> GetCustomer(string customerId)
{
  try
  {
    var customerResponse = await this._container.ReadItemAsync<Customer>(customerId, new PartitionKey(customerId));
    return customerResponse;
  }
  catch (CosmosException ex) 
  {
    Console.WriteLine("Exception occured in GetCustomer: {0} Message body is {1}.\n", ex.Message,ex.ResponseBody);
    throw ;
   }
}