close_incoming

        # Ractor.close_incoming

(from ruby core)
---
    ractor.close_incoming -> true | false

---

Closes the incoming port and returns its previous state. All further
attempts to Ractor.receive in the ractor, and #send to the ractor will
fail with Ractor::ClosedError.

    r = Ractor.new {sleep(500)}
    r.close_incoming  #=> false
    r.close_incoming  #=> true
    r.send('test')
    # Ractor::ClosedError (The incoming-port is already closed)