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.go

@@ -30,7 +30,7 @@ const metadataCtxKey ctxKey = 0
 // New returns a context and cancel function for a given task message.
 func New(msg *base.TaskMessage, deadline time.Time) (context.Context, context.CancelFunc) {
 	metadata := taskMetadata{
-		id:         msg.ID.String(),
+		id:         msg.ID,
 		maxRetry:   msg.Retry,
 		retryCount: msg.Retried,
 		qname:      msg.Queue,

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)