public interface ITask { Task Start(); void Cancel(); }In this example, the ITask interface provides two methods: Start, which starts the task, and Cancel, which cancels the task. This interface could be implemented in a variety of ways, depending on the application needs. It is often used in conjunction with the CancellationToken class from the System.Threading namespace. Package library: The package library for this example would be the .NET Framework or .NET Core, as they both provide the necessary classes and interfaces for asynchronous programming in C#.