sync_async.rb

require 'open-uri'

@files =
[
  'file_example_JPG_1MB.jpg',
  'file_example_GIF_1MB.gif',
  'file_example_PNG_1MB.png'
]

def sync
  t = Time.now
  @files.each do |file|
    File.open(file, 'w') do |_file|
      _file.write(open("https://file-examples-com.github.io/uploads/2017/10/#{file}").read)
    end
  end
  puts Time.now - t
end

def async
  t = Time.now
  @files.map do |file|
    Thread.new do
      File.open(file, 'w') do |_file|
        _file.write(open("https://file-examples-com.github.io/uploads/2017/10/#{file}").read)
      end
    end
  end.map(&:join)
  puts Time.now - t
end

# sync
async