async-barrier.rb

require "async"
require "async/barrier"

Async do |task|
  barrier = Async::Barrier.new

  barrier.async do
    puts "Inside task 1"
    sleep 20
    puts "Task 1 done"
  end

  barrier.async do
    puts "Inside task 2"
    sleep 10
    puts "Task 2 done"
  end

  barrier.async do
    puts "Inside task 3"
    sleep 2
    puts "Task 3 done"
  end

  puts "Waiting"
  barrier.wait

  puts "Done"
end