diff --git a/.github/labeler.yml b/.github/labeler.yml
index 3846a6b5..e1658383 100644
--- a/.github/labeler.yml
+++ b/.github/labeler.yml
@@ -9,7 +9,3 @@ ruby:
 ruby_h_to_go:
   - changed-files:
       - any-glob-to-any-file: "_tools/ruby_h_to_go/**/*"
-
-patch_for_go_gem:
-  - changed-files:
-      - any-glob-to-any-file: "_tools/patch_for_go_gem/**/*"
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e3bbb026..99c59880 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -14,7 +14,6 @@ on:
       - ".github/pages.yml"
       - ".github/release.yml"
       - ".github/workflows/labeler.yml"
-      - ".github/workflows/patch_for_go_gem.yml"
       - ".github/workflows/rbs-collection-updater.yml"
       - "_benchmark/**"
 
diff --git a/.github/workflows/patch_for_go_gem.yml b/.github/workflows/patch_for_go_gem.yml
deleted file mode 100644
index 294b49f1..00000000
--- a/.github/workflows/patch_for_go_gem.yml
+++ /dev/null
@@ -1,85 +0,0 @@
-name: patch_for_go_gem
-
-on:
-  push:
-    branches:
-      - main
-  pull_request:
-    types:
-      - opened
-      - synchronize
-      - reopened
-    paths:
-      - ".github/workflows/patch_for_go_gem.yml"
-      - "_tools/patch_for_go_gem/**"
-      - "Gemfile"
-      - "Gemfile.lock"
-
-defaults:
-  run:
-    working-directory: _tools/patch_for_go_gem/
-
-jobs:
-  generate-matrix:
-    runs-on: ubuntu-latest
-
-    outputs:
-      matrix: ${{ steps.set-matrix.outputs.matrix }}
-
-    steps:
-      - uses: actions/checkout@v5
-
-      - id: set-matrix
-        run: echo "matrix=$(cat matrix.json | jq -c)" >> $GITHUB_OUTPUT
-        working-directory: .github/workflows/
-
-  test:
-    name: "test (Go ${{ matrix.go }}, Ruby ${{ matrix.ruby }})"
-
-    needs:
-      - generate-matrix
-
-    runs-on: ubuntu-latest
-
-    strategy:
-      fail-fast: false
-
-      matrix: ${{ fromJSON(needs.generate-matrix.outputs.matrix) }}
-
-    steps:
-      - uses: actions/checkout@v5
-
-      - uses: actions/setup-go@v6
-        with:
-          go-version: ${{ matrix.go }}
-
-      - uses: ruby/setup-ruby@v1
-        with:
-          ruby-version: ${{ matrix.ruby }}
-          bundler-cache: true
-
-      - run: bundle exec rspec
-
-      - name: Slack Notification (not success)
-        uses: act10ns/slack@v2
-        if: "! success()"
-        continue-on-error: true
-        with:
-          status: ${{ job.status }}
-          webhook-url: ${{ secrets.SLACK_WEBHOOK }}
-          matrix: ${{ toJson(matrix) }}
-
-  notify:
-    needs:
-      - test
-
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Slack Notification (success)
-        uses: act10ns/slack@v2
-        if: always()
-        continue-on-error: true
-        with:
-          status: ${{ job.status }}
-          webhook-url: ${{ secrets.SLACK_WEBHOOK }}
diff --git a/README.md b/README.md
index 0560eb33..b0a08902 100644
--- a/README.md
+++ b/README.md
@@ -23,20 +23,11 @@
 See [.github/workflows/matrix.json](.github/workflows/matrix.json) for details
 
 ## Getting started
-At first, patch to make a gem into a Go gem right after `bundle gem`
+Run followings
 
-See [_tools/patch_for_go_gem/](_tools/patch_for_go_gem/)
-
-Please also add the following depending on the CI you are using.
-
-### GitHub Actions
-e.g.
-
-```yml
-- uses: actions/setup-go@v5
-  with:
-    go-version-file: ext/GEM_NAME/go.mod
-```
+1. `bundle gem <GEM_NAME> --ext=go` **(Requires bundler v4.0.0.beta1+)**
+2. `bundle install`
+3. `bundle exec rake go:mod_tidy`
 
 ## Implementing Ruby methods in Go
 For example, consider the following Ruby method implemented in Go
diff --git a/Rakefile b/Rakefile
index ddaf280b..36c90aa2 100644
--- a/Rakefile
+++ b/Rakefile
@@ -25,6 +25,6 @@ task :changelog, [:before, :after] do |_, params|
   sh "ruby _tools/changelog_generator/changelog_generator.rb #{args.join(" ")}"
 end
 
-task build_all: %w[ruby:build_all go:build_all go_gem:test ruby_h_to_go:test patch_for_go_gem:test]
+task build_all: %w[ruby:build_all go:build_all go_gem:test ruby_h_to_go:test]
 
 task default: :build_all
diff --git a/_gem/README.md b/_gem/README.md
index 6bc26503..0291b699 100644
--- a/_gem/README.md
+++ b/_gem/README.md
@@ -10,10 +10,6 @@ Add below.
 spec.add_dependency "go_gem"
 ```
 
-See below for details.
-
-[/_tools/patch_for_go_gem/](/_tools/patch_for_go_gem/)
-
 ## Usage
 ### [`create_go_makefile`](https://ruby-go-gem.github.io/go-gem-wrapper/GoGem/Mkmf.html#create_go_makefile-instance_method)
 `create_go_makefile` is an extension of `create_makefile`.
diff --git a/_tasks/patch_for_go_gem.rake b/_tasks/patch_for_go_gem.rake
deleted file mode 100644
index 6f3382db..00000000
--- a/_tasks/patch_for_go_gem.rake
+++ /dev/null
@@ -1,10 +0,0 @@
-# frozen_string_literal: true
-
-namespace :patch_for_go_gem do
-  desc "Run _tools/patch_for_go_gem test"
-  task :test do
-    Dir.chdir(File.join(repo_root, "_tools", "patch_for_go_gem")) do
-      sh "rspec"
-    end
-  end
-end
diff --git a/_tools/patch_for_go_gem/.gitignore b/_tools/patch_for_go_gem/.gitignore
deleted file mode 100644
index e3200e0f..00000000
--- a/_tools/patch_for_go_gem/.gitignore
+++ /dev/null
@@ -1,56 +0,0 @@
-*.gem
-*.rbc
-/.config
-/coverage/
-/InstalledFiles
-/pkg/
-/spec/reports/
-/spec/examples.txt
-/test/tmp/
-/test/version_tmp/
-/tmp/
-
-# Used by dotenv library to load environment variables.
-# .env
-
-# Ignore Byebug command history file.
-.byebug_history
-
-## Specific to RubyMotion:
-.dat*
-.repl_history
-build/
-*.bridgesupport
-build-iPhoneOS/
-build-iPhoneSimulator/
-
-## Specific to RubyMotion (use of CocoaPods):
-#
-# We recommend against adding the Pods directory to your .gitignore. However
-# you should judge for yourself, the pros and cons are mentioned at:
-# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
-#
-# vendor/Pods/
-
-## Documentation cache and generated files:
-/.yardoc/
-/_yardoc/
-/doc/
-/rdoc/
-
-## Environment normalization:
-/.bundle/
-/vendor/bundle
-/lib/bundler/man/
-
-# for a library or gem, you might want to ignore these files since the code is
-# intended to run in multiple environments; otherwise, check them in:
-# Gemfile.lock
-# .ruby-version
-# .ruby-gemset
-
-# unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
-.rvmrc
-
-# Used by RuboCop. Remote config files pulled in from inherit_from directive.
-# .rubocop-https?--*
diff --git a/_tools/patch_for_go_gem/.rspec b/_tools/patch_for_go_gem/.rspec
deleted file mode 100644
index 5be63fcb..00000000
--- a/_tools/patch_for_go_gem/.rspec
+++ /dev/null
@@ -1,2 +0,0 @@
---require spec_helper
---format documentation
diff --git a/_tools/patch_for_go_gem/README.md b/_tools/patch_for_go_gem/README.md
deleted file mode 100644
index eb758bff..00000000
--- a/_tools/patch_for_go_gem/README.md
+++ /dev/null
@@ -1,20 +0,0 @@
-# patch_for_go_gem
-Patch to make a gem into a Go gem right after `bundle gem`
-
-> [!NOTE]
-> This is a temporary tool until `bundle gem --ext=go` is added to the bundler
->
-> c.f. https://github.com/rubygems/rubygems/pull/8183
-
-## Requirements
-* Go 1.23+
-* Ruby 3.3+
-
-## Usage
-1. Download [patch_for_go_gem.rb](patch_for_go_gem.rb)
-2. Run `bundle gem <GEM_NAME> --ext=c`
-    * The other options for `bundle gem` are optional
-3. Run `ruby patch_for_go_gem.rb --file /path/to/GEM_NAME.gemspec --dry-run`
-4. Run `ruby patch_for_go_gem.rb --file /path/to/GEM_NAME.gemspec`
-5. `cd` to the same location as `ext/GEM_NAME/go.mod`
-6. Run `go get -u github.com/ruby-go-gem/go-gem-wrapper@latest`
diff --git a/_tools/patch_for_go_gem/patch_for_go_gem.rb b/_tools/patch_for_go_gem/patch_for_go_gem.rb
deleted file mode 100644
index 6b6af93b..00000000
--- a/_tools/patch_for_go_gem/patch_for_go_gem.rb
+++ /dev/null
@@ -1,199 +0,0 @@
-# frozen_string_literal: true
-
-require "optparse"
-
-gemspec_file = nil
-dry_run = false
-
-opt = OptionParser.new
-opt.on("-f", "--file=GEMSPEC_FILE") { |v| gemspec_file = v }
-opt.on("--dry-run") { |v| dry_run = v }
-
-opt.parse!(ARGV)
-
-raise "--file is required" unless gemspec_file
-raise "#{gemspec_file} isn't gemspec" unless File.extname(gemspec_file) == ".gemspec"
-raise "#{gemspec_file} isn't found" unless File.exist?(gemspec_file)
-
-# Patch to make a gem into a Go gem right after `bundle gem`
-class GemPatcher # rubocop:disable Metrics/ClassLength
-  attr_reader :gemspec_file
-
-  # @param gemspec_file [String]
-  # @param dry_run [Boolean]
-  def initialize(gemspec_file:, dry_run:)
-    @gemspec_file = gemspec_file
-    @dry_run = dry_run
-  end
-
-  def perform
-    create_gem_name_go
-    create_go_mod
-    update_gem_name_c
-    update_extconf_rb
-    update_gemspec
-  end
-
-  private
-
-  # @return [Boolean]
-  def dry_run?
-    @dry_run
-  end
-
-  # @return [String] path to ext dir. (e.g. /path/to/gem_name/ext/gem_name)
-  def ext_dir
-    File.join(File.absolute_path(File.dirname(gemspec_file)), "ext", gem_name)
-  end
-
-  # @return [String]
-  def gem_name
-    File.basename(gemspec_file, ".gemspec")
-  end
-
-  # @return [String]
-  def module_name
-    snake_to_camel(gem_name)
-  end
-
-  # @param str [String]
-  # @return [String]
-  def snake_to_camel(str)
-    str.split("_").map(&:capitalize).join.gsub(/(?<=\d)([a-z])/) { _1.upcase } # rubocop:disable Style/SymbolProc
-  end
-
-  # Create <gem_name>.go
-  def create_gem_name_go
-    gem_name_go_path = File.join(ext_dir, "#{gem_name}.go")
-
-    return if File.exist?(gem_name_go_path)
-
-    content = <<~GO
-      package main
-
-      /*
-      #include "#{gem_name}.h"
-      */
-      import "C"
-
-      import (
-      \t"github.com/ruby-go-gem/go-gem-wrapper/ruby"
-      )
-
-      //export Init_#{gem_name}
-      func Init_#{gem_name}() {
-      \trb_m#{module_name} := ruby.RbDefineModule("#{module_name}")
-      }
-
-      func main() {
-      }
-    GO
-
-    save_file(file_path: gem_name_go_path, content:)
-  end
-
-  def create_go_mod
-    go_mod_path = File.join(ext_dir, "go.mod")
-
-    return if File.exist?(go_mod_path)
-
-    `go version` =~ /go version go([.\d]+)/
-    go_version = ::Regexp.last_match(1)
-
-    raise "go isn't found in PATH" unless go_version
-
-    content = <<~GO
-      module github.com/username/#{gem_name}
-
-      go #{go_version}
-    GO
-
-    save_file(file_path: go_mod_path, content:)
-  end
-
-  def update_gem_name_c
-    gem_name_c_path = File.join(ext_dir, "#{gem_name}.c")
-
-    content = File.read(gem_name_c_path)
-
-    return if content.include?('#include "_cgo_export.h"')
-
-    content = <<~C
-      #include "#{gem_name}.h"
-      #include "_cgo_export.h"
-    C
-
-    save_file(file_path: gem_name_c_path, content:)
-  end
-
-  def update_extconf_rb
-    extconf_rb_path = File.join(ext_dir, "extconf.rb")
-
-    content = File.read(extconf_rb_path)
-
-    unless content.include?(%(require "go_gem/mkmf"))
-      content.gsub!(<<~RUBY, <<~RUBY)
-        require "mkmf"
-      RUBY
-        require "mkmf"
-        require "go_gem/mkmf"
-      RUBY
-    end
-
-    unless content.include?(%(create_go_makefile("#{gem_name}/#{gem_name}")))
-      content.gsub!(<<~RUBY, <<~RUBY)
-        create_makefile("#{gem_name}/#{gem_name}")
-      RUBY
-        create_go_makefile("#{gem_name}/#{gem_name}")
-      RUBY
-    end
-
-    save_file(file_path: extconf_rb_path, content:)
-  end
-
-  def update_gemspec
-    content = File.read(gemspec_file)
-
-    return if content.include?(%(.add_dependency "go_gem")) || content.include?(%(.add_runtime_dependency "go_gem"))
-
-    content =~ /Gem::Specification\.new\s+do\s+\|(.+)\|/
-    spec_var_name = ::Regexp.last_match(1)
-
-    content.gsub!(/^end\n/, <<~RUBY)
-        #{spec_var_name}.add_dependency "go_gem"
-      end
-    RUBY
-
-    save_file(file_path: gemspec_file, content:)
-  end
-
-  # @param file_path [String]
-  # @param content [String]
-  def save_file(file_path:, content:)
-    is_updated = File.exist?(file_path)
-    if is_updated
-      before_content = File.read(file_path)
-      return if content == before_content
-    end
-
-    if dry_run?
-      if is_updated
-        puts "[INFO] #{file_path} will be updated (dry-run)"
-      else
-        puts "[INFO] #{file_path} will be created (dry-run)"
-      end
-
-      return
-    end
-
-    File.binwrite(file_path, content)
-
-    if is_updated
-      puts "[INFO] #{file_path} is updated"
-    else
-      puts "[INFO] #{file_path} is created"
-    end
-  end
-end
-
-GemPatcher.new(gemspec_file:, dry_run:).perform
diff --git a/_tools/patch_for_go_gem/spec/patch_for_go_gem_spec.rb b/_tools/patch_for_go_gem/spec/patch_for_go_gem_spec.rb
deleted file mode 100644
index 22579198..00000000
--- a/_tools/patch_for_go_gem/spec/patch_for_go_gem_spec.rb
+++ /dev/null
@@ -1,108 +0,0 @@
-# frozen_string_literal: true
-
-RSpec.describe "patch_for_go_gem.rb" do
-  gem_name = "new_gem"
-
-  before(:all) do
-    @temp_dir = Dir.mktmpdir
-
-    Dir.chdir(@temp_dir) do
-      sh "bundle gem #{gem_name} --ext=c"
-      sh "ruby #{File.join(src_dir, "patch_for_go_gem.rb")} --file=#{File.join(gem_name, "#{gem_name}.gemspec")}"
-
-      if ENV["CI"]
-        [
-          "#{gem_name}.c",
-          "#{gem_name}.go",
-          "go.mod",
-          "extconf.rb",
-        ].each do |file_name|
-          file_path = File.join(gem_name, "ext", gem_name, file_name)
-          puts "----------------------------------------"
-          puts file_path
-          puts "----------------------------------------"
-          puts File.read(file_path)
-          puts ""
-        end
-      end
-    end
-  end
-
-  # @param command [String]
-  def sh(command)
-    puts "$ #{command}"
-    system command, exception: true
-  end
-
-  after(:all) do
-    FileUtils.remove_entry_secure(@temp_dir) if @temp_dir && Dir.exist?(@temp_dir)
-  end
-
-  around do |example|
-    Dir.chdir(@temp_dir) do
-      example.run
-    end
-  end
-
-  describe file(File.join(gem_name, "ext", gem_name, "#{gem_name}.c")) do
-    it { should be_file }
-    it { should exist }
-    its(:content) { should match(/^#include "_cgo_export.h"$/) }
-    its(:content) { should_not match(/VALUE\s*rb/) }
-    its(:content) { should_not include "RUBY_FUNC_EXPORTED void" }
-    its(:content) { should_not match(/Init_.+\(void\)/) }
-    its(:content) { should_not match(/rb_m.+\s*=\s*rb_define_module\(".+"\);/) }
-  end
-
-  describe file(File.join(gem_name, "ext", gem_name, "#{gem_name}.go")) do
-    it { should be_file }
-    it { should exist }
-
-    let(:content) do
-      <<~GO
-        package main
-
-        /*
-        #include "#{gem_name}.h"
-        */
-        import "C"
-
-        import (
-        \t"github.com/ruby-go-gem/go-gem-wrapper/ruby"
-        )
-      GO
-    end
-
-    its(:content) { should be_start_with content }
-  end
-
-  describe file(File.join(gem_name, "ext", gem_name, "go.mod")) do
-    it { should be_file }
-    it { should exist }
-
-    let(:content) do
-      <<~GO
-        module github.com/username/#{gem_name}
-
-      GO
-    end
-
-    its(:content) { should be_start_with content }
-  end
-
-  describe file(File.join(gem_name, "ext", gem_name, "extconf.rb")) do
-    it { should be_file }
-    it { should exist }
-
-    its(:content) { should include %(require "go_gem/mkmf") }
-    its(:content) { should include %(create_go_makefile("#{gem_name}/#{gem_name}")) }
-    its(:content) { should_not include %(create_makefile("#{gem_name}/#{gem_name}")) }
-  end
-
-  describe file(File.join(gem_name, "#{gem_name}.gemspec")) do
-    it { should be_file }
-    it { should exist }
-
-    its(:content) { should include %(spec.add_dependency "go_gem") }
-  end
-end
diff --git a/_tools/patch_for_go_gem/spec/spec_helper.rb b/_tools/patch_for_go_gem/spec/spec_helper.rb
deleted file mode 100644
index 1ac3aa94..00000000
--- a/_tools/patch_for_go_gem/spec/spec_helper.rb
+++ /dev/null
@@ -1,118 +0,0 @@
-# frozen_string_literal: true
-
-# This file was generated by the `rspec --init` command. Conventionally, all
-# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
-# The generated `.rspec` file contains `--require spec_helper` which will cause
-# this file to always be loaded, without a need to explicitly require it in any
-# files.
-#
-# Given that it is always loaded, you are encouraged to keep this file as
-# light-weight as possible. Requiring heavyweight dependencies from this file
-# will add to the boot time of your test suite on EVERY test run, even for an
-# individual file that may not need all of that loaded. Instead, consider making
-# a separate helper file that requires the additional dependencies and performs
-# the additional setup, and require it from the spec files that actually need
-# it.
-#
-# See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
-
-require "tmpdir"
-require "serverspec"
-
-set :backend, :exec
-
-RSpec.configure do |config|
-  # rspec-expectations config goes here. You can use an alternate
-  # assertion/expectation library such as wrong or the stdlib/minitest
-  # assertions if you prefer.
-  config.expect_with :rspec do |expectations|
-    # This option will default to `true` in RSpec 4. It makes the `description`
-    # and `failure_message` of custom matchers include text for helper methods
-    # defined using `chain`, e.g.:
-    #     be_bigger_than(2).and_smaller_than(4).description
-    #     # => "be bigger than 2 and smaller than 4"
-    # ...rather than:
-    #     # => "be bigger than 2"
-    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
-  end
-
-  # rspec-mocks config goes here. You can use an alternate test double
-  # library (such as bogus or mocha) by changing the `mock_with` option here.
-  config.mock_with :rspec do |mocks|
-    # Prevents you from mocking or stubbing a method that does not exist on
-    # a real object. This is generally recommended, and will default to
-    # `true` in RSpec 4.
-    mocks.verify_partial_doubles = true
-  end
-
-  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
-  # have no way to turn it off -- the option exists only for backwards
-  # compatibility in RSpec 3). It causes shared context metadata to be
-  # inherited by the metadata hash of host groups and examples, rather than
-  # triggering implicit auto-inclusion in groups with matching metadata.
-  config.shared_context_metadata_behavior = :apply_to_host_groups
-
-  # The settings below are suggested to provide a good initial experience
-  # with RSpec, but feel free to customize to your heart's content.
-  #   # This allows you to limit a spec run to individual examples or groups
-  #   # you care about by tagging them with `:focus` metadata. When nothing
-  #   # is tagged with `:focus`, all examples get run. RSpec also provides
-  #   # aliases for `it`, `describe`, and `context` that include `:focus`
-  #   # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
-  #   config.filter_run_when_matching :focus
-  #
-  #   # Allows RSpec to persist some state between runs in order to support
-  #   # the `--only-failures` and `--next-failure` CLI options. We recommend
-  #   # you configure your source control system to ignore this file.
-  #   config.example_status_persistence_file_path = "spec/examples.txt"
-  #
-  #   # Limits the available syntax to the non-monkey patched syntax that is
-  #   # recommended. For more details, see:
-  #   # https://rspec.info/features/3-12/rspec-core/configuration/zero-monkey-patching-mode/
-  #   config.disable_monkey_patching!
-  #
-  #   # This setting enables warnings. It's recommended, but in some cases may
-  #   # be too noisy due to issues in dependencies.
-  #   config.warnings = true
-  #
-  #   # Many RSpec users commonly either run the entire suite or an individual
-  #   # file, and it's useful to allow more verbose output when running an
-  #   # individual spec file.
-  #   if config.files_to_run.one?
-  #     # Use the documentation formatter for detailed output,
-  #     # unless a formatter has already been configured
-  #     # (e.g. via a command-line flag).
-  #     config.default_formatter = "doc"
-  #   end
-  #
-  #   # Print the 10 slowest examples and example groups at the
-  #   # end of the spec run, to help surface which specs are running
-  #   # particularly slow.
-  #   config.profile_examples = 10
-  #
-  #   # Run specs in random order to surface order dependencies. If you find an
-  #   # order dependency and want to debug it, you can fix the order by providing
-  #   # the seed, which is printed after each run.
-  #   #     --seed 1234
-  #   config.order = :random
-  #
-  #   # Seed global randomization in this process using the `--seed` CLI option.
-  #   # Setting this allows you to use `--seed` to deterministically reproduce
-  #   # test failures related to randomization by passing the same `--seed` value
-  #   # as the one that triggered the failure.
-  #   Kernel.srand config.seed
-
-  config.define_derived_metadata do |meta|
-    meta[:aggregate_failures] = true
-  end
-end
-
-# @return [Pathname]
-def spec_dir
-  __dir__
-end
-
-# @return [Pathname]
-def src_dir
-  File.expand_path(File.join(spec_dir, ".."))
-end