IOError: closed stream for SFTP Download in Ruby on Rails

here is my code

def get_usage      host = Rails.application.secrets.sonet_sftp_host      account = Rails.application.secrets.sonet_sftp_account      result_repo = "/home/jpmb_mobile/commreport/volume"      Net::SFTP.start(host, account) do |sftp|        sftp.dir.glob(result_repo, "REPORT_MOBILE_VOLUME*").each do |file|          puts file.name          date = file.name.gsub(/REPORT_MOBILE_VOLUME_/, '')[0..7].to_date          time = file.name.gsub(/REPORT_MOBILE_VOLUME_/, '')[8..9]          last_usage = SonetUsage.last          next if last_usage.present? and ( last_usage.usage_date > date or (last_usage.usage_date == date and last_usage.usage_time.to_i >= time.to_i))          file_data = sftp.download!("#{result_repo}/#{file.name}")          CSV.parse(file_data, headers: false, col_sep: ",") do |row|            tel_no = '0'+ row[0].gsub(/^81/, '')            today_usage_high = row[1].to_i            yesterday_usage_high = row[2].to_i            before_yesterday_usage_high = row[3].to_i            today_usage_low = row[4].to_i - row[1].to_i            yesterday_usage_low = row[5].to_i - row[2].to_i            before_yesterday_usage_low = row[6].to_i - row[3].to_i            puts tel_no            card = SonetCard.where(tel_no: tel_no, status: [:activating, :stop, :cancelled, :cancelling]).last            if card.nil?              puts "not found!"              next            end            before_yesterday_records = SonetUsage.where(sonet_card: card, usage_date: date - 2.days)            yesterday_records = SonetUsage.where(sonet_card: card, usage_date: date - 1.days)            today_records = SonetUsage.where(sonet_card: card, usage_date: date)            if (before_yesterday_records.empty? or before_yesterday_records.last.usage_time != "24") and (before_yesterday_usage_high != 0 or before_yesterday_usage_low != 0)              by_usage = SonetUsage.find_or_create_by(sonet_card: card, usage_date: date - 2.days, usage_time: "24")              by_usage.update(total_bytes_high: before_yesterday_usage_high - before_yesterday_records.try("sum", :total_bytes_high).to_i, total_bytes_low: before_yesterday_usage_low - before_yesterday_records.try("sum", :total_bytes_low).to_i)            end            if (yesterday_records.empty? or yesterday_records.last.usage_time != "24") and (yesterday_usage_high != 0 or yesterday_usage_low != 0)              y_usage = SonetUsage.find_or_create_by(sonet_card: card, usage_date: date - 1.days, usage_time: "24")              y_usage.update(total_bytes_low: yesterday_usage_low - yesterday_records.try("sum", :total_bytes_low).to_i, total_bytes_high: yesterday_usage_high - yesterday_records.try("sum", :total_bytes_high).to_i)            end            if time != "00" and ( today_usage_high != 0 or today_usage_low != 0 ) and (today_records.empty? or today_records.last.usage_time != time)              t_usage = SonetUsage.find_or_create_by(sonet_card: card, usage_date: date, usage_time: time)              t_usage.update(total_bytes_low: today_usage_low - today_records.try("sum", :total_bytes_low).to_i, total_bytes_high: today_usage_high - today_records.try("sum", :total_bytes_high).to_i)            end          end        end      end    end

Am getting this IOError: closed stream for SFTP Download in Ruby on Rails constantly,I don't have any idea how to fix this.I even tried to give StringIO.new but it is not working as expectedHow can I complete my action.Please help?