channel.rb

class Channel < SizedQueue
  def initialize
    super(1)
  end
end

channel = Channel.new

Thread.new(channel) do |ch|
  val = rand(3.0) + 1.0
  sleep val
  ch.push val
end

puts channel.pop

golike.rb

require 'concurrent/mvar'

q1 = Concurrent::MVar.new
q2 = Concurrent::MVar.new

def work
  sleep rand(3.0)
end

Thread.new(q1) { |q| q.put work }
Thread.new(q2) { |q| q.put work }

result = [q1.take, q2.take]

puts result

promise.rb

class Promise
  def initialize(*args, &block)
    @thread = Thread.new(args) do |a|
      @value = yield *a
    end
  end

  def value
    @thread.join
    @value
  end
end

def work
  sleep rand(3.0)
end

promises = []

100.times do
 promises << Promise.new { work }
end

result = promises.map(&:value)

puts result