Introduce Task Results

* Added Retention Option to specify retention TTL for tasks
* Added ResultWriter as a client interface to write result data for the associated task

internal/context/context_test.go

@@ -29,7 +29,6 @@ func TestCreateContextWithFutureDeadline(t *testing.T) {
 		}
 
 		ctx, cancel := New(msg, tc.deadline)
-
 		select {
 		case x := <-ctx.Done():
 			t.Errorf("<-ctx.Done() == %v, want nothing (it should block)", x)