disconnect

# File lib/net/imap.rb, line 316
    def disconnect
      begin
        begin
          # try to call SSL::SSLSocket#io.
          @sock.io.shutdown
        rescue NoMethodError
          # @sock is not an SSL::SSLSocket.
          @sock.shutdown
        end
      rescue Errno::ENOTCONN
        # ignore `Errno::ENOTCONN: Socket is not connected' on some platforms.
      rescue Exception => e
        @receiver_thread.raise(e)
      end
      @receiver_thread.join
      synchronize do
        @sock.close
      end
      raise e if e
    end