I used the code from the documentation riker.rs/patterns and made it work.
Tested with cargo 1.53.0 (4369396ce 2021-04-27) on macOS 10.15.7 (19H1217).
Example output:
2021-07-18 01:06:51+00:00 DEBG [riker::system] Starting actor system: System[riker]
2021-07-18 01:06:51+00:00 DEBG [riker::system] Actor system [b6c7c06f-bfbe-4640-8754-7cb54e7b1279] [riker] started
The result value is: 200
Process finished with exit code 0
MIT License.