class ActiveStorage::Service::S3Service

def stream(key)

Reads the object for the given key in chunks, yielding each to the block. 
def stream(key)
  object = object_for(key)
  chunk_size = 5.megabytes
  offset = 0
  raise ActiveStorage::FileNotFoundError unless object.exists?
  while offset < object.content_length
    yield object.get(range: "bytes=#{offset}-#{offset + chunk_size - 1}").body.string.force_encoding(Encoding::BINARY)
    offset += chunk_size
  end
end