static void Main(string[] args)
{
string apiKey;
using (StreamReader reader = new StreamReader("api-secret.txt"))
{
apiKey = reader.ReadToEnd();
}
ExchangeRate er = new ExchangeRate(apiKey);
Console.WriteLine("ExchangeRate API is {0}.", er.HealthCheck() ? "working" : "not working");
//er.GetAllExchangeRatesInPeriod(from: DateTime.Today.AddDays(-5), to: DateTime.Today.AddDays(-1));
}