code: function loadFromFile(filename) {
    var cfg = {}
    Object.assign(
      cfg,
      loadDefault(),
      JSON.parse(fs.readFileSync(filename))
    )
  
    return cfg
  }
docs: Get HTTP server configuration from JSON file.
  @param {string} filename - The JSON filename.
  @throws Will throw an error if invalid filename or JSON.
  @return {Object} The HTTP server configuration.