class Google::Cloud::Config

def self.credentials_from_env *vars
  vars.each do |var|
    data = ::ENV[var]
    next unless data
    str = data.strip
    return str if ::File.file? str
    json = begin
             ::JSON.parse str
           rescue ::StandardError
             nil
           end
    return json if json.is_a? ::Hash
  end
  nil
end