avatar_uploader.rb

class AvatarUploader < CarrierWave::Uploader::Base

  # Include RMagick or MiniMagick support:
  # include CarrierWave::RMagick
  include CarrierWave::MiniMagick
  
  if Rails.env.production?
    storage :fog
  else
    storage :file
  end

end

carrierwave.rb

CarrierWave.configure do |config|
  config.fog_credentials = {
    provider: 'AWS',
    aws_access_key_id: ENV['AWS_ACCESS_KEY_ID'],
    aws_secret_access_key: ENV['AWS_SECRET_ACCESS_KEY'],
    region: ENV['AWS_S3_REGION'],
    path_style: true
  }
  config.fog_directory = ENV['S3_BUCKET_NAME']
end