diff --git a/Gemfile b/Gemfile
deleted file mode 100644
index 6592888..0000000
--- a/Gemfile
+++ /dev/null
@@ -1,4 +0,0 @@
-source 'https://rubygems.org'
-
-# Specify your gem's dependencies in seisan.gemspec
-gemspec
diff --git a/README.md b/README.md
index 2e0017d..01fdd50 100644
--- a/README.md
+++ b/README.md
@@ -4,28 +4,14 @@ Seisan solution for small team.
 
 ## Installation
 
-You need a few steps to setup seisan data repository. `example` directory in `enishitech/seisan` will be a good reference for you.
-
-Put `Gemfile`:
-
-```
-source 'https://rubygems.org'
+Compile from Source.
 
-gem 'rake'
-gem 'seisan'
 ```
-
-Run bundler:
-
-```shell
-% bundle
+% go get -u github.com/enishitech/seisan
 ```
 
-Put `Rakefile`:
+You need a few steps to setup seisan data repository. `example` directory in `enishitech/seisan` will be a good reference for you.
 
-```
-require 'seisan/task'
-```
 Create `data` directory to store data.
 
 ```shell
@@ -35,7 +21,7 @@ Create `data` directory to store data.
 OK, now everything is set up. Run
 
 ```shell
-% bundle exec rake seisan TARGET=2013/07
+% seisan 2013/07
 ```
 
 Then you will have an empty monthly report (because you have no record in seisan data) at `output/2013-07.xlsx`.
@@ -83,12 +69,10 @@ data
         └── 08-shidara.yaml
 ```
 
-Put `Rakefile` to your seisan data repository,
-
 Then you can generate seisan report.
 
 ```shell
-% bundle exec rake seisan TARGET=2013/07
+% seisan 2013/07
 ```
 
 ## Contributing
@@ -101,8 +85,7 @@ Then you can generate seisan report.
 
 -----
 
-© 2013 Enishi Tech Inc.
-
+© 2015 Enishi Tech Inc.
 
 [![Bitdeli Badge](https://d2weczhvl823v0.cloudfront.net/enishitech/seisan/trend.png)](https://bitdeli.com/free "Bitdeli Badge")
 
diff --git a/Rakefile b/Rakefile
deleted file mode 100644
index 2995527..0000000
--- a/Rakefile
+++ /dev/null
@@ -1 +0,0 @@
-require "bundler/gem_tasks"
diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..0885604
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,35 @@
+package config
+
+import (
+	"io/ioutil"
+	"os"
+
+	"gopkg.in/yaml.v2"
+)
+
+type Config struct {
+	Organization
+}
+
+type Organization struct {
+	Name string
+}
+
+func Load(configPath string) (*Config, error) {
+	var config Config
+
+	_, err := os.Stat(configPath)
+	if err != nil {
+		return nil, err
+	}
+
+	buf, err := ioutil.ReadFile(configPath)
+	if err != nil {
+		return nil, err
+	}
+	err = yaml.Unmarshal(buf, &config)
+	if err != nil {
+		return nil, err
+	}
+	return &config, nil
+}
diff --git a/example/Gemfile b/example/Gemfile
deleted file mode 100644
index 1d2db71..0000000
--- a/example/Gemfile
+++ /dev/null
@@ -1,9 +0,0 @@
-source 'https://rubygems.org'
-
-gem 'rake'
-
-# Use development version. Usually you should want to use released version:
-#
-# gem 'seisan'
-#
-gem 'seisan', path: '..'
diff --git a/example/Rakefile b/example/Rakefile
deleted file mode 100644
index 1f0a334..0000000
--- a/example/Rakefile
+++ /dev/null
@@ -1 +0,0 @@
-require 'seisan/task'
diff --git a/expense/expense.go b/expense/expense.go
new file mode 100644
index 0000000..b1b8773
--- /dev/null
+++ b/expense/expense.go
@@ -0,0 +1,8 @@
+package expense
+
+type Entry struct {
+	Date      string
+	Applicant string
+	Amount    int
+	Remarks   string
+}
diff --git a/expense/reporter.go b/expense/reporter.go
new file mode 100644
index 0000000..2177a0d
--- /dev/null
+++ b/expense/reporter.go
@@ -0,0 +1,101 @@
+package expense
+
+import (
+	"sort"
+
+	"github.com/tealeg/xlsx"
+
+	"github.com/enishitech/seisan/config"
+	"github.com/enishitech/seisan/request"
+)
+
+type ExpenseReporter struct{}
+
+func NewReporter() *ExpenseReporter {
+	return &ExpenseReporter{}
+}
+
+type ExpenseRequest struct {
+	Applicant       string  `yaml:"applicant"`
+	ExpeneseEntries []Entry `yaml:"expense"`
+}
+
+func (reporter ExpenseReporter) renderSummary(sheet *xlsx.Sheet, sumByApplicant map[string]int) {
+	var row *xlsx.Row
+	var cell *xlsx.Cell
+
+	row = sheet.AddRow()
+	cell = row.AddCell()
+	cell.SetValue("立替払サマリー")
+	row = sheet.AddRow()
+	for _, heading := range []string{"氏名", "金額"} {
+		cell = row.AddCell()
+		cell.SetValue(heading)
+	}
+	for key, value := range sumByApplicant {
+		row = sheet.AddRow()
+		cell = row.AddCell()
+		cell.SetValue(key)
+		cell = row.AddCell()
+		cell.SetValue(value)
+	}
+	row = sheet.AddRow()
+	cell = row.AddCell()
+	cell.SetValue("")
+}
+
+type ByDate []Entry
+
+func (a ByDate) Len() int           { return len(a) }
+func (a ByDate) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a ByDate) Less(i, j int) bool { return a[i].Date < a[j].Date }
+
+func (reporter ExpenseReporter) renderEntries(sheet *xlsx.Sheet, entries []Entry) {
+	var row *xlsx.Row
+	var cell *xlsx.Cell
+
+	row = sheet.AddRow()
+	cell = row.AddCell()
+	cell.SetValue("立替払明細")
+	row = sheet.AddRow()
+	for _, heading := range []string{"日付", "立替者", "金額", "摘要", "備考"} {
+		cell = row.AddCell()
+		cell.SetValue(heading)
+	}
+	for _, detail := range entries {
+		row = sheet.AddRow()
+		cell = row.AddCell()
+		cell.SetValue(detail.Date)
+		cell = row.AddCell()
+		cell.SetValue(detail.Applicant)
+		cell = row.AddCell()
+		cell.SetValue(detail.Amount)
+		cell = row.AddCell()
+		cell.SetValue(detail.Remarks)
+	}
+}
+
+func (reporter ExpenseReporter) Report(sheet *xlsx.Sheet, conf *config.Config, requests []request.Request) error {
+	entries := make([]Entry, 0)
+	sumByApplicant := make(map[string]int)
+	for _, req := range requests {
+		var er ExpenseRequest
+		if err := req.Unmarshal(&er); err != nil {
+			return err
+		}
+		if _, ok := sumByApplicant[er.Applicant]; !ok {
+			sumByApplicant[er.Applicant] = 0
+		}
+		for _, entry := range er.ExpeneseEntries {
+			entry.Applicant = er.Applicant
+			sumByApplicant[er.Applicant] += entry.Amount
+			entries = append(entries, entry)
+		}
+	}
+	sort.Sort(ByDate(entries))
+
+	reporter.renderSummary(sheet, sumByApplicant)
+	reporter.renderEntries(sheet, entries)
+
+	return nil
+}
diff --git a/lib/seisan.rb b/lib/seisan.rb
deleted file mode 100644
index 6e2188b..0000000
--- a/lib/seisan.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require 'seisan/version'
-require 'seisan/report'
-require 'seisan/base_renderer'
-require 'seisan/header_renderer'
-require 'seisan/expense_renderer'
-require 'logger'
-
-module Seisan
-  def self.logger
-    @@logger ||= initialize_default_logger
-  end
-
-  def self.logger=(logger)
-    @@logger = logger
-  end
-
-  def self.initialize_default_logger
-    logger = Logger.new(STDOUT)
-    logger.formatter = proc{|severity, datetime, progname, message|
-      "#{message}\n"
-    }
-    logger
-  end
-end
diff --git a/lib/seisan/base_renderer.rb b/lib/seisan/base_renderer.rb
deleted file mode 100644
index 002cf13..0000000
--- a/lib/seisan/base_renderer.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-module Seisan
-  class BaseRenderer
-    def initialize(requests, sheet, font, config)
-      @requests = requests
-      @sheet = sheet
-      @font = font
-      @config = config
-    end
-
-    def requests
-      @requests
-    end
-
-    def row(columns=[])
-      @sheet.add_row columns, :style => @font
-    end
-  end
-end
diff --git a/lib/seisan/expense_renderer.rb b/lib/seisan/expense_renderer.rb
deleted file mode 100644
index 5bad39f..0000000
--- a/lib/seisan/expense_renderer.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-require 'seisan/base_renderer'
-require 'date'
-
-module Seisan
-  class ExpenseRenderer < BaseRenderer
-    def render
-      row ['立替払サマリー']
-      row summary_headings
-      summary.each do |person, amount|
-        row [person, amount]
-      end
-      row
-
-      row ['立替払明細']
-      row headings
-      lines.each do |line|
-        row line
-      end
-      row
-
-      Seisan.logger.info 'Processed %d expenses' % lines.size
-    end
-
-    private
-    def summary_headings
-      %w(氏名 金額)
-    end
-
-    def summary
-      summary = Hash.new(0)
-      requests.each do |entry|
-        summary[entry['applicant']] += entry['expense'].inject(0){|r, e| r += e['amount'].to_i }
-      end
-      summary
-    end
-
-    def headings
-      %w(日付 立替者 金額 摘要 備考)
-    end
-
-    def lines
-      lines = []
-      requests.each do |entry|
-        entry['expense'].each do |expense|
-          lines << [expense['date'].to_s, entry['applicant'], expense['amount'], expense['remarks'], expense['notes']]
-        end
-      end
-      lines.sort_by {|line| [Date.parse(line[0]), line[1]] }
-    end
-  end
-end
diff --git a/lib/seisan/header_renderer.rb b/lib/seisan/header_renderer.rb
deleted file mode 100644
index d69c988..0000000
--- a/lib/seisan/header_renderer.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require 'seisan/base_renderer'
-
-module Seisan
-  class HeaderRenderer < BaseRenderer
-    def render
-      row ["#{organization_name} 精算シート #{target_name}"]
-      row ['作成時刻', Time.now.strftime('%Y-%m-%d %X')]
-      row
-    end
-
-    private
-    def target_name
-      @config['target']
-    end
-
-    def organization_name
-      @config['organization'] ? @config['organization']['name'] : ''
-    end
-  end
-end
diff --git a/lib/seisan/report.rb b/lib/seisan/report.rb
deleted file mode 100644
index 70bd8ed..0000000
--- a/lib/seisan/report.rb
+++ /dev/null
@@ -1,59 +0,0 @@
-require 'axlsx'
-require 'fileutils'
-require 'seisan/header_renderer'
-require 'seisan/expense_renderer'
-
-module Seisan
-  class Report
-    DEFAULT_RENDERERS = [
-      Seisan::HeaderRenderer,
-      Seisan::ExpenseRenderer
-    ]
-    @@renderers = DEFAULT_RENDERERS
-
-    class << self
-      def renderer_chain(&block)
-        @@renderers = []
-        block.call(self) if block
-      end
-
-      def add(renderer)
-        @@renderers << renderer
-      end
-    end
-
-    def initialize(requests, config)
-      @requests = requests
-      @config = config
-    end
-
-    def export(dest_path)
-      prepare_sheet
-
-      renderers.each do |renderer|
-        renderer.render
-      end
-
-      write_to_file(dest_path)
-    end
-
-    private
-    def renderers
-      @@renderers.map {|r| r.new(@requests, @sheet, @font, @config) }
-    end
-
-    def prepare_sheet
-      @package = Axlsx::Package.new
-      @workbook = @package.workbook
-      @package.use_shared_strings = true
-      @font = @workbook.styles.add_style :font_name => 'ＭＳ Ｐゴシック'
-      @sheet = @workbook.add_worksheet(:name => '精算シート')
-    end
-
-    def write_to_file(dest_path)
-      FileUtils.mkdir_p(File.dirname(dest_path))
-      @package.serialize(dest_path)
-      Seisan.logger.info 'Wrote to %s' % dest_path
-    end
-  end
-end
diff --git a/lib/seisan/task.rb b/lib/seisan/task.rb
deleted file mode 100644
index 0ebfb18..0000000
--- a/lib/seisan/task.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require 'rake'
-require 'seisan'
-require 'gimlet'
-
-module Seisan
-  class Task
-    include Rake::DSL if defined? Rake::DSL
-    def self.install_tasks
-      new.install
-    end
-
-    def install
-      desc "Generate seisan report"
-      task :seisan do
-        src_dir, dest_dir = 'data', 'output'
-        config = user_config.merge('target' => ENV['TARGET'])
-        report(src_dir, dest_dir, config)
-      end
-      task :default => :seisan
-    end
-
-    private
-    def report(src_dir, dest_dir, config)
-      if config['target'].nil?
-        Seisan.logger.error "You must specify the 'TARGET'.\nExample:\n  % bundle exec rake TARGET=2013/07"
-        exit
-      end
-
-      Seisan.logger.info 'Processing %s ...' % config['target']
-      requests = load_seisan_requests(src_dir, config['target'])
-      Seisan.logger.info 'Loaded %d files' % requests.size
-      report = Seisan::Report.new(requests, config)
-
-      dest_path = File.join(dest_dir, '%s.xlsx' % convert_target_to_file_name(config['target']))
-      report.export(dest_path)
-    end
-
-    def user_config
-      Gimlet::DataStore.new('config.yaml').to_h
-    rescue Gimlet::DataStore::SourceNotFound
-      {}
-    end
-
-    def load_seisan_requests(src_dir, target)
-      source = Gimlet::DataStore.new(File.join(src_dir, target))
-      source.to_h.values
-    rescue Gimlet::DataStore::SourceNotFound
-      []
-    end
-
-    def convert_target_to_file_name(target)
-      target.gsub('/', '-')
-    end
-  end
-end
-
-# Install tasks
-Seisan::Task.install_tasks
diff --git a/lib/seisan/version.rb b/lib/seisan/version.rb
deleted file mode 100644
index 686865f..0000000
--- a/lib/seisan/version.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-module Seisan
-  VERSION = "0.0.1"
-end
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..13a4df0
--- /dev/null
+++ b/main.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/codegangsta/cli"
+
+	"github.com/enishitech/seisan/expense"
+	"github.com/enishitech/seisan/reporter"
+)
+
+func main() {
+	app := cli.NewApp()
+	app.Name = "seisan"
+	app.Usage = "Generate seisan report"
+
+	sr := reporter.New(*expense.NewReporter())
+
+	app.Action = func(c *cli.Context) {
+		args := c.Args()
+		if !args.Present() {
+			fmt.Println("You must specify the 'TARGET'.\nExample:\n  % seisan 2015/10")
+			return
+		}
+
+		target := args.First()
+		fmt.Printf("Processing %s ...\n", target)
+		if err := sr.Report(".", target); err != nil {
+			log.Fatal(err)
+		}
+	}
+	app.Run(os.Args)
+}
diff --git a/reporter/reporter.go b/reporter/reporter.go
new file mode 100644
index 0000000..6a4b580
--- /dev/null
+++ b/reporter/reporter.go
@@ -0,0 +1,93 @@
+package reporter
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/tealeg/xlsx"
+
+	"github.com/enishitech/seisan/config"
+	"github.com/enishitech/seisan/request"
+)
+
+type Reporter interface {
+	Report(*xlsx.Sheet, *config.Config, []request.Request) error
+}
+
+type SeisanReporter struct {
+	reporters []Reporter
+}
+
+func New(reporters ...Reporter) *SeisanReporter {
+	sr := &SeisanReporter{}
+	sr.reporters = reporters
+	return sr
+}
+
+func renderReportHeader(sheet *xlsx.Sheet, orgName, name string) {
+	var row *xlsx.Row
+	var cell *xlsx.Cell
+
+	row = sheet.AddRow()
+	cell = row.AddCell()
+	cell.SetValue(orgName + " 精算シート " + name)
+	row = sheet.AddRow()
+	cell = row.AddCell()
+	cell.SetValue("作成時刻")
+	cell = row.AddCell()
+	cell.SetValue(time.Now())
+	row = sheet.AddRow()
+	cell = row.AddCell()
+}
+
+func (sr SeisanReporter) Report(baseDir string, target string) error {
+	dataDir := filepath.Join(baseDir, "data")
+	outputDir := filepath.Join(baseDir, "output")
+	configPath := filepath.Join(baseDir, "config.yaml")
+	targetDir := filepath.Join(dataDir, target)
+
+	conf, err := config.Load(configPath)
+	if err != nil {
+		return err
+	}
+
+	reqs, err := request.LoadDir(targetDir)
+	if err != nil {
+		return err
+	}
+
+	targetName := strings.Replace(target, "/", "-", -1)
+	xlsx.SetDefaultFont(11, "ＭＳ Ｐゴシック")
+
+	file := xlsx.NewFile()
+	sheet, err := file.AddSheet("精算シート")
+	if err != nil {
+		return err
+	}
+
+	renderReportHeader(sheet, targetName, conf.Organization.Name)
+
+	for _, r := range sr.reporters {
+		err := r.Report(sheet, conf, reqs)
+		if err != nil {
+			return err
+		}
+	}
+
+	destPath := filepath.Join(outputDir, targetName+".xlsx")
+	if _, err := os.Stat(outputDir); os.IsNotExist(err) {
+		if err := os.Mkdir(outputDir, 0777); err != nil {
+			return err
+		}
+	}
+	err = file.Save(destPath)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Wrote to %s\n", destPath)
+
+	return nil
+}
diff --git a/request/request.go b/request/request.go
new file mode 100644
index 0000000..700e113
--- /dev/null
+++ b/request/request.go
@@ -0,0 +1,39 @@
+package request
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+
+	"gopkg.in/yaml.v2"
+)
+
+type Request struct {
+	Data []byte
+}
+
+func (req *Request) Unmarshal(v interface{}) error {
+	return yaml.Unmarshal(req.Data, v)
+}
+
+func LoadDir(dir string) ([]Request, error) {
+	entries, err := ioutil.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	requests := []Request{}
+
+	for _, entry := range entries {
+		path := filepath.Join(dir, entry.Name())
+		data, err := ioutil.ReadFile(path)
+		if err != nil {
+			return nil, err
+		}
+
+		request := Request{Data: data}
+		requests = append(requests, request)
+	}
+	fmt.Printf("Loaded %d files\n", len(entries))
+
+	return requests, nil
+}
diff --git a/seisan.gemspec b/seisan.gemspec
deleted file mode 100644
index d98f584..0000000
--- a/seisan.gemspec
+++ /dev/null
@@ -1,26 +0,0 @@
-# coding: utf-8
-lib = File.expand_path('../lib', __FILE__)
-$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require 'seisan/version'
-
-Gem::Specification.new do |spec|
-  spec.name          = "seisan"
-  spec.version       = Seisan::VERSION
-  spec.authors       = ["SHIMADA Koji"]
-  spec.email         = ["koji.shimada@enishi-tech.com"]
-  spec.description   = %q{seisan solution for small team}
-  spec.summary       = %q{seisan solution for small team}
-  spec.homepage      = "https://github.com/enishitech/seisan"
-  spec.license       = "MIT"
-
-  spec.files         = `git ls-files`.split($/)
-  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
-  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
-  spec.require_paths = ["lib"]
-
-  spec.add_runtime_dependency "axlsx", "~> 2.0.1"
-  spec.add_runtime_dependency "gimlet", "~> 0.0.3"
-
-  spec.add_development_dependency "bundler", "~> 1.3"
-  spec.add_development_dependency "rake"
-end