play.cr

enum Control
    Done
end

class Worker(T)
    def initialize
        @channel = Channel(T|Control).new(10)
        @done = Channel(Control).new
    end

    def add(item : T)
        @channel.send(item)
    end

    def run
        spawn {
            loop do
                item = @channel.receive
                case item
                when T
                    puts "I got #{item}"
                when Control
                    @done.send(item)
                    break
                end
            end
        }
    end

    def done
        @channel.send(Control::Done)
    end

    def join
        puts "waiting"
        @done.receive
    end
end


w = Worker(Int32).new
w.run
w.add 2
w.add 1
w.add 3
w.done
w.join
puts "Done"