You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: secret_token.rb
    path of file: ./repos/sample_apps/4_0/ch08/config/initializers
    
    the code of the file until where you have to start completion: # Be sure to restart your server when you modify this file.

# Your secret key is used for verifying the integrity of 
    
def secure_token
  token_file = Rails.root.join('.secret')
  if File.exist?(token_file)
    # Use the existing token.
    File.read(token_file).chomp
  else
    # Generate a new token and store it in token_file.
    token = SecureRandom.hex(64)
    File.write(token_file, token)
    token
  end