diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index d3d4091..3c9e844 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -19,10 +19,10 @@ jobs:
           - gemfiles/faraday_0.15.gemfile
           - gemfiles/faraday_0.16.gemfile
           - gemfiles/faraday_0.17.gemfile
-
+          - gemfiles/faraday_1.0.gemfile
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-ruby@v1
+      - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
       - uses: actions/cache@v2
@@ -31,20 +31,28 @@ jobs:
           key: ${{ runner.os }}-gems-${{ matrix.ruby }}-${{ matrix.gemfile }}-${{ hashFiles('faraday_middleware-aws-sigv4.gemspec', '**/Gemfile', '${{ matrix.gemfile }}') }}
           restore-keys: |
             ${{ runner.os }}-gems-${{ matrix.ruby }}-${{ matrix.gemfile }}-
-
       - name: Setup dependencies
         run: |
           bundle config path vendor/bundle
           bundle install
         env:
           BUNDLE_GEMFILE: ${{ matrix.gemfile }}
-
       - name: Run tests
         run: ${{ matrix.env }} bundle exec rake
         env:
           BUNDLE_GEMFILE: ${{ matrix.gemfile }}
-
-      - name: Coveralls GitHub Action
+      - name: Coveralls Parallel
+        uses: coverallsapp/github-action@v1.1.2
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          flag-name: run-${{ matrix.ruby }}-${{ matrix.env }}-${{ matrix.gemfile }}
+          parallel: true
+  finish:
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Coveralls Finished
         uses: coverallsapp/github-action@v1.1.2
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
+          parallel-finished: true
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..652b1c3
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,16 @@
+AllCops:
+  Exclude:
+    - 'gemfiles/**/*'
+  TargetRubyVersion: 2.4
+  NewCops: enable
+Bundler/OrderedGems:
+  Include:
+    - 'Appraisals'
+Metrics/BlockLength:
+  Enabled: false
+Layout/LineLength:
+  Enabled: false
+Metrics/MethodLength:
+  Enabled: false
+Style/Documentation:
+  Enabled: false
diff --git a/.simplecov b/.simplecov
index 2c60eb6..c350579 100644
--- a/.simplecov
+++ b/.simplecov
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 SimpleCov.start do
   # exclude directories and files
-  add_filter "/spec/"
+  add_filter '/spec/'
 end
diff --git a/Appraisals b/Appraisals
index 7d2f06d..0d768bf 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 appraise 'faraday-0.15' do
   gem 'faraday', '~> 0.15.0'
 end
diff --git a/Gemfile b/Gemfile
index ec1ce2c..8ae2f52 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Specify your gem's dependencies in faraday_middleware-aws-sigv4.gemspec
diff --git a/Rakefile b/Rakefile
index 93cb943..a2c92fd 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,6 +1,13 @@
+# frozen_string_literal: true
+
 require 'bundler/gem_tasks'
 require 'rspec/core/rake_task'
+require 'rubocop/rake_task'
 
 RSpec::Core::RakeTask.new(:spec)
 
-task :default => :spec
+RuboCop::RakeTask.new do |task|
+  task.options = %w[-c .rubocop.yml]
+end
+
+task default: %i[rubocop spec]
diff --git a/bin/console b/bin/console
deleted file mode 100755
index 7264b67..0000000
--- a/bin/console
+++ /dev/null
@@ -1,14 +0,0 @@
-#!/usr/bin/env ruby
-
-require "bundler/setup"
-require "faraday_middleware/aws/sigv4"
-
-# You can add fixtures and/or initialization code here to make experimenting
-# with your gem easier. You can also use a different console, if you like.
-
-# (If you use this, don't forget to add pry to your Gemfile!)
-# require "pry"
-# Pry.start
-
-require "irb"
-IRB.start(__FILE__)
diff --git a/bin/setup b/bin/setup
deleted file mode 100755
index dce67d8..0000000
--- a/bin/setup
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-IFS=$'\n\t'
-set -vx
-
-bundle install
-
-# Do any other automated setup that you need to do here
diff --git a/faraday_middleware-aws-sigv4.gemspec b/faraday_middleware-aws-sigv4.gemspec
index 86b4bb0..5beb3be 100644
--- a/faraday_middleware-aws-sigv4.gemspec
+++ b/faraday_middleware-aws-sigv4.gemspec
@@ -1,5 +1,6 @@
-# coding: utf-8
-lib = File.expand_path('../lib', __FILE__)
+# frozen_string_literal: true
+
+lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
 Gem::Specification.new do |spec|
@@ -8,8 +9,8 @@ Gem::Specification.new do |spec|
   spec.authors       = ['Genki Sugawara']
   spec.email         = ['sugawara@cookpad.com']
 
-  spec.summary       = %q{Faraday middleware for AWS Signature Version 4 using aws-sigv4.}
-  spec.description   = %q{Faraday middleware for AWS Signature Version 4 using aws-sigv4.}
+  spec.summary       = 'Faraday middleware for AWS Signature Version 4 using aws-sigv4.'
+  spec.description   = 'Faraday middleware for AWS Signature Version 4 using aws-sigv4.'
   spec.homepage      = 'https://github.com/winebarrel/faraday_middleware-aws-sigv4'
   spec.license       = 'MIT'
 
@@ -20,18 +21,21 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.3'
+  spec.required_ruby_version = '>= 2.4'
 
-  spec.add_dependency 'faraday', '>= 0.15'
   spec.add_dependency 'aws-sigv4', '~> 1.0'
+  spec.add_dependency 'faraday', '>= 0.15'
 
-  spec.add_development_dependency 'faraday_middleware'
+  spec.add_development_dependency 'appraisal', '>= 2.2'
+  spec.add_development_dependency 'aws-sdk-core', '~> 3.14.0'
   spec.add_development_dependency 'bundler'
+  spec.add_development_dependency 'faraday_middleware'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'rspec', '~> 3.0'
-  spec.add_development_dependency 'timecop'
-  spec.add_development_dependency 'aws-sdk-core', '~> 3.14.0'
-  spec.add_development_dependency 'appraisal', '>= 2.2'
+  spec.add_development_dependency 'rubocop', '>= 1.8.0'
+  spec.add_development_dependency 'rubocop-rake'
+  spec.add_development_dependency 'rubocop-rspec'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'simplecov-lcov'
+  spec.add_development_dependency 'timecop'
 end
diff --git a/lib/faraday_middleware/aws_sigv4.rb b/lib/faraday_middleware/aws_sigv4.rb
index 6994851..8e1beae 100644
--- a/lib/faraday_middleware/aws_sigv4.rb
+++ b/lib/faraday_middleware/aws_sigv4.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 require 'faraday'
 
 module FaradayMiddleware
   autoload :AwsSigV4, 'faraday_middleware/request/aws_sigv4'
-  Faraday::Request.register_middleware aws_sigv4: lambda { AwsSigV4 }
+  Faraday::Request.register_middleware aws_sigv4: -> { AwsSigV4 }
 end
diff --git a/lib/faraday_middleware/request/aws_sigv4.rb b/lib/faraday_middleware/request/aws_sigv4.rb
index be093ee..3c3779a 100644
--- a/lib/faraday_middleware/request/aws_sigv4.rb
+++ b/lib/faraday_middleware/request/aws_sigv4.rb
@@ -1,37 +1,41 @@
+# frozen_string_literal: true
+
 require 'aws-sigv4'
 require 'faraday_middleware/request/aws_sigv4_util'
 
-class FaradayMiddleware::AwsSigV4 < Faraday::Middleware
-  include FaradayMiddleware::AwsSigV4Util
+module FaradayMiddleware
+  class AwsSigV4 < Faraday::Middleware
+    include FaradayMiddleware::AwsSigV4Util
 
-  def initialize(app, options = nil)
-    super(app)
-    @signer = Aws::Sigv4::Signer.new(options)
-    @options = options
-  end
+    def initialize(app, options = nil)
+      super(app)
+      @signer = Aws::Sigv4::Signer.new(options)
+      @options = options
+    end
 
-  def call(env)
-    sign!(env)
-    @app.call(env)
-  end
+    def call(env)
+      sign!(env)
+      @app.call(env)
+    end
 
-  private
+    private
 
-  def sign!(env)
-    request = build_aws_sigv4_request(env)
-    signature = @signer.sign_request(request)
+    def sign!(env)
+      request = build_aws_sigv4_request(env)
+      signature = @signer.sign_request(request)
 
-    signature.headers.each do |name, value|
-      env.request_headers[name] = value
+      signature.headers.each do |name, value|
+        env.request_headers[name] = value
+      end
     end
-  end
 
-  def build_aws_sigv4_request(env)
-    {
-      http_method: env.method.to_s,
-      url: seahorse_encode_query(env.url),
-      headers: env.request_headers,
-      body: env.body,
-    }
+    def build_aws_sigv4_request(env)
+      {
+        http_method: env.method.to_s,
+        url: seahorse_encode_query(env.url),
+        headers: env.request_headers,
+        body: env.body
+      }
+    end
   end
 end
diff --git a/lib/faraday_middleware/request/aws_sigv4_util.rb b/lib/faraday_middleware/request/aws_sigv4_util.rb
index 5a7237d..4ddfdba 100644
--- a/lib/faraday_middleware/request/aws_sigv4_util.rb
+++ b/lib/faraday_middleware/request/aws_sigv4_util.rb
@@ -1,32 +1,36 @@
-module FaradayMiddleware::AwsSigV4Util
-  def seahorse_encode_query(url)
-    return url unless url.query
+# frozen_string_literal: true
 
-    params = URI.decode_www_form(url.query)
+module FaradayMiddleware
+  module AwsSigV4Util
+    def seahorse_encode_query(url)
+      return url unless url.query
 
-    if params.any? {|_, v| v[?\s] }
-      url = url.dup
-      url.query = seahorse_encode_www_form(params)
-    end
+      params = URI.decode_www_form(url.query)
 
-    url
-  end
+      if params.any? { |_, v| v["\s"] }
+        url = url.dup
+        url.query = seahorse_encode_www_form(params)
+      end
 
-  def seahorse_encode_www_form(params)
-    params.flat_map {|key, value|
-      encoded_key = URI.encode_www_form_component(key)
+      url
+    end
 
-      if value.nil?
-        encoded_key
-      else
-        Array(value).map do |v|
-          if v.nil?
-            # nothing to do
-          else
-            encoded_key + '=' + Aws::Sigv4::Signer.uri_escape(v)
+    def seahorse_encode_www_form(params)
+      params.flat_map do |key, value|
+        encoded_key = URI.encode_www_form_component(key)
+
+        if value.nil?
+          encoded_key
+        else
+          Array(value).map do |v|
+            if v.nil?
+              # nothing to do
+            else
+              "#{encoded_key}=#{Aws::Sigv4::Signer.uri_escape(v)}"
+            end
           end
         end
-      end
-    }.join(?&)
+      end.join('&')
+    end
   end
 end
diff --git a/spec/faraday_middleware/aws_sigv4_instance_profile_credentials_spec.rb b/spec/faraday_middleware/aws_sigv4_instance_profile_credentials_spec.rb
index 4b11ae6..acdd5d9 100644
--- a/spec/faraday_middleware/aws_sigv4_instance_profile_credentials_spec.rb
+++ b/spec/faraday_middleware/aws_sigv4_instance_profile_credentials_spec.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 RSpec.describe FaradayMiddleware::AwsSigV4 do
-  def faraday(options = {})
+  def faraday(options = {}, &block)
     options = {
       url: 'https://apigateway.us-east-1.amazonaws.com'
     }.merge(options)
@@ -8,47 +10,45 @@ def faraday(options = {})
       aws_sigv4_options = {
         service: 'apigateway',
         region: 'us-east-1',
-        credentials_provider: Aws::InstanceProfileCredentials.new,
+        credentials_provider: Aws::InstanceProfileCredentials.new
       }
 
       faraday.request :aws_sigv4, aws_sigv4_options
-      faraday.response :json, :content_type => /\bjson\b/
+      faraday.response :json, content_type: /\bjson\b/
 
-      faraday.adapter(:test, Faraday::Adapter::Test::Stubs.new) do |stub|
-        yield(stub)
-      end
+      faraday.adapter(:test, Faraday::Adapter::Test::Stubs.new, &block)
     end
   end
 
   let(:response) do
-    {'accountUpdate'=>
-      {'name'=>nil,
-       'template'=>false,
-       'templateSkipList'=>nil,
-       'title'=>nil,
-       'updateAccountInput'=>nil},
-     'cloudwatchRoleArn'=>nil,
-     'self'=>
-      {'__type'=>
+    { 'accountUpdate' =>
+      { 'name' => nil,
+        'template' => false,
+        'templateSkipList' => nil,
+        'title' => nil,
+        'updateAccountInput' => nil },
+      'cloudwatchRoleArn' => nil,
+      'self' =>
+      { '__type' =>
         'GetAccountRequest:http://internal.amazon.com/coral/com.amazonaws.backplane.controlplane/',
-       'name'=>nil,
-       'template'=>false,
-       'templateSkipList'=>nil,
-       'title'=>nil},
-     'throttleSettings'=>{'burstLimit'=>1000, 'rateLimit'=>500.0}}
+        'name' => nil,
+        'template' => false,
+        'templateSkipList' => nil,
+        'title' => nil },
+      'throttleSettings' => { 'burstLimit' => 1000, 'rateLimit' => 500.0 } }
   end
 
   let(:expected_headers) do
-    {'User-Agent'=>"Faraday v#{Faraday::VERSION}",
-     'host'=>'apigateway.us-east-1.amazonaws.com',
-     'x-amz-content-sha256'=>
-      'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'}
+    { 'User-Agent' => "Faraday v#{Faraday::VERSION}",
+      'host' => 'apigateway.us-east-1.amazonaws.com',
+      'x-amz-content-sha256' =>
+      'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855' }
   end
 
   let(:authz_tmpl) do
-    'AWS4-HMAC-SHA256 Credential=%{access_key_id}/20150101/us-east-1/apigateway/aws4_request, ' +
-    "SignedHeaders=host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-security-token, " +
-    "Signature=%{signature}"
+    'AWS4-HMAC-SHA256 Credential=%<access_key_id>s/20150101/us-east-1/apigateway/aws4_request, ' \
+      'SignedHeaders=host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-security-token, ' \
+      'Signature=%<signature>s'
   end
 
   before do
@@ -56,11 +56,11 @@ def faraday(options = {})
 
     allow_any_instance_of(Aws::InstanceProfileCredentials).to receive(:get_credentials) {
       JSON.dump({
-        'AccessKeyId' => "akid#{Time.now.to_i}",
-        'SecretAccessKey' => "secret#{Time.now.to_i}",
-        'Token' => "token#{Time.now.to_i}",
-        'Expiration' => Time.now + 3600,
-      })
+                  'AccessKeyId' => "akid#{Time.now.to_i}",
+                  'SecretAccessKey' => "secret#{Time.now.to_i}",
+                  'Token' => "token#{Time.now.to_i}",
+                  'Expiration' => Time.now + 3600
+                })
     }
   end
 
@@ -70,26 +70,24 @@ def faraday(options = {})
     client = faraday do |stub|
       stub.get('/account') do |env|
         account_headers = env.request_headers
-        [200, {'Content-Type' => 'application/json'}, JSON.dump(response)]
+        [200, { 'Content-Type' => 'application/json' }, JSON.dump(response)]
       end
     end
 
     expect(client.get('/account').body).to eq response
 
     expect(account_headers).to include expected_headers.update(
-     'x-amz-date' => '20150101T000000Z',
-     'x-amz-security-token' => 'token1420070400',
+      'x-amz-date' => '20150101T000000Z',
+      'x-amz-security-token' => 'token1420070400'
     )
 
-    expect(account_headers.fetch('authorization')).to match Regexp.new(authz_tmpl % {
-      access_key_id: 'akid1420070400',
-      signature: '(' + %w(
-        8a7679e7f6e14faa3c5bc8e585f16416bba04883767b651169f745e987908c04
-        0593f7578c038c94d3d463d5b1ed0fa8b4c4f5525c7abb08ae6c095d9df5fb61
-        bb9d431b7be57abce9d81b4b4fd62036eec4d9d4e9dc44ad95b1166a8b16c3f4
-        3dd176d303ac2227e8522eb13413670657821280569556d289047e6ae2ccd975
-      ).join('|') + ')',
-    })
+    expect(account_headers.fetch('authorization')).to match Regexp.new(format(authz_tmpl, access_key_id: 'akid1420070400', signature: "(#{%w[
+      8a7679e7f6e14faa3c5bc8e585f16416bba04883767b651169f745e987908c04
+      0593f7578c038c94d3d463d5b1ed0fa8b4c4f5525c7abb08ae6c095d9df5fb61
+      bb9d431b7be57abce9d81b4b4fd62036eec4d9d4e9dc44ad95b1166a8b16c3f4
+      3dd176d303ac2227e8522eb13413670657821280569556d289047e6ae2ccd975
+      14af79b17c4e94c9582512125daa97f19b19b04d0b8d605d68a02bded3948770
+    ].join('|')})"))
 
     # 50 minutes after
     Timecop.travel(Time.now + 3000)
@@ -97,19 +95,17 @@ def faraday(options = {})
     expect(client.get('/account').body).to eq response
 
     expect(account_headers).to include expected_headers.update(
-     'x-amz-date' => '20150101T005000Z',
-     'x-amz-security-token' => 'token1420070400',
+      'x-amz-date' => '20150101T005000Z',
+      'x-amz-security-token' => 'token1420070400'
     )
 
-    expect(account_headers.fetch('authorization')).to match Regexp.new(authz_tmpl % {
-      access_key_id: 'akid1420070400',
-      signature: '(' + %w(
-        936d7c18c31135cb0baebe62ada628644a4c24efcadce044ceb650bc04e3fe1d
-        891f865c1a1297ed133589cd2abb575fd998b66cf79a0505941f50ef3405576b
-        816c7f811b60426fb2cd232ae3a5c6568f5150058bdaa99e3233b61fe8ab7668
-        053ed3702ade746b97a3aeba3f4bfdd06154b0c7d0cc50fa9ba3db81385f6110
-      ).join('|') + ')',
-    })
+    expect(account_headers.fetch('authorization')).to match Regexp.new(format(authz_tmpl, access_key_id: 'akid1420070400', signature: "(#{%w[
+      936d7c18c31135cb0baebe62ada628644a4c24efcadce044ceb650bc04e3fe1d
+      891f865c1a1297ed133589cd2abb575fd998b66cf79a0505941f50ef3405576b
+      816c7f811b60426fb2cd232ae3a5c6568f5150058bdaa99e3233b61fe8ab7668
+      053ed3702ade746b97a3aeba3f4bfdd06154b0c7d0cc50fa9ba3db81385f6110
+      8ac6851c02183ca987e91116262c9afe24662aff4a7f2dcb67b8d9212cd2d4ba
+    ].join('|')})"))
 
     # 10 minutes after
     Timecop.travel(Time.now + 600)
@@ -117,18 +113,16 @@ def faraday(options = {})
     expect(client.get('/account').body).to eq response
 
     expect(account_headers).to include expected_headers.update(
-     'x-amz-date' => '20150101T010000Z',
-     'x-amz-security-token' => 'token1420074000',
+      'x-amz-date' => '20150101T010000Z',
+      'x-amz-security-token' => 'token1420074000'
     )
 
-    expect(account_headers.fetch('authorization')).to match Regexp.new(authz_tmpl % {
-      access_key_id: 'akid1420074000',
-      signature: '(' + %w(
-        42b4050c22d246f66c13357186a87bb2891ea0bebf7663cec398f9a12d869133
-        f264df5cb2359d8b9d491ff48bd57237d9260f01ebf638455ca18c3dab8beb2d
-        7e8b319cb3ab3d36bd4a6b34d411c03f88891d2266adcc9498573c4ee33d2088
-        dca2842cb07926a4929af3708165ca2897207ca729cab19c1deb518d5d492848
-      ).join('|') + ')',
-    })
+    expect(account_headers.fetch('authorization')).to match Regexp.new(format(authz_tmpl, access_key_id: 'akid1420074000', signature: "(#{%w[
+      42b4050c22d246f66c13357186a87bb2891ea0bebf7663cec398f9a12d869133
+      f264df5cb2359d8b9d491ff48bd57237d9260f01ebf638455ca18c3dab8beb2d
+      7e8b319cb3ab3d36bd4a6b34d411c03f88891d2266adcc9498573c4ee33d2088
+      dca2842cb07926a4929af3708165ca2897207ca729cab19c1deb518d5d492848
+      c17ee288dfc7e4598e333765b85e0305959ba33835453b7c2885b7d43aabb4f2
+    ].join('|')})"))
   end
 end
diff --git a/spec/faraday_middleware/aws_sigv4_spec.rb b/spec/faraday_middleware/aws_sigv4_spec.rb
index 6555c84..1b18199 100644
--- a/spec/faraday_middleware/aws_sigv4_spec.rb
+++ b/spec/faraday_middleware/aws_sigv4_spec.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 RSpec.describe FaradayMiddleware::AwsSigV4 do
-  def faraday(options = {})
+  def faraday(options = {}, &block)
     options = {
       url: 'https://apigateway.us-east-1.amazonaws.com'
     }.merge(options)
@@ -9,34 +11,32 @@ def faraday(options = {})
         service: 'apigateway',
         region: 'us-east-1',
         access_key_id: 'akid',
-        secret_access_key: 'secret',
+        secret_access_key: 'secret'
       }
 
       faraday.request :aws_sigv4, aws_sigv4_options
-      faraday.response :json, :content_type => /\bjson\b/
+      faraday.response :json, content_type: /\bjson\b/
 
-      faraday.adapter(:test, Faraday::Adapter::Test::Stubs.new) do |stub|
-        yield(stub)
-      end
+      faraday.adapter(:test, Faraday::Adapter::Test::Stubs.new, &block)
     end
   end
 
   let(:response) do
-    {'accountUpdate'=>
-      {'name'=>nil,
-       'template'=>false,
-       'templateSkipList'=>nil,
-       'title'=>nil,
-       'updateAccountInput'=>nil},
-     'cloudwatchRoleArn'=>nil,
-     'self'=>
-      {'__type'=>
+    { 'accountUpdate' =>
+      { 'name' => nil,
+        'template' => false,
+        'templateSkipList' => nil,
+        'title' => nil,
+        'updateAccountInput' => nil },
+      'cloudwatchRoleArn' => nil,
+      'self' =>
+      { '__type' =>
         'GetAccountRequest:http://internal.amazon.com/coral/com.amazonaws.backplane.controlplane/',
-       'name'=>nil,
-       'template'=>false,
-       'templateSkipList'=>nil,
-       'title'=>nil},
-     'throttleSettings'=>{'burstLimit'=>1000, 'rateLimit'=>500.0}}
+        'name' => nil,
+        'template' => false,
+        'templateSkipList' => nil,
+        'title' => nil },
+      'throttleSettings' => { 'burstLimit' => 1000, 'rateLimit' => 500.0 } }
   end
 
   let(:signed_headers) do
@@ -44,15 +44,15 @@ def faraday(options = {})
   end
 
   let(:default_expected_headers) do
-    {'User-Agent'=>"Faraday v#{Faraday::VERSION}",
-     'host'=>'apigateway.us-east-1.amazonaws.com',
-     'x-amz-date'=>'20150101T000000Z',
-     'x-amz-content-sha256'=>
+    { 'User-Agent' => "Faraday v#{Faraday::VERSION}",
+      'host' => 'apigateway.us-east-1.amazonaws.com',
+      'x-amz-date' => '20150101T000000Z',
+      'x-amz-content-sha256' =>
       'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855',
-     'authorization'=>
-      'AWS4-HMAC-SHA256 Credential=akid/20150101/us-east-1/apigateway/aws4_request, ' +
-      "SignedHeaders=#{signed_headers}, " +
-      "Signature=#{signature}"}
+      'authorization' =>
+      'AWS4-HMAC-SHA256 Credential=akid/20150101/us-east-1/apigateway/aws4_request, ' \
+        "SignedHeaders=#{signed_headers}, " \
+        "Signature=#{signature}" }
   end
 
   let(:additional_expected_headers) { {} }
@@ -68,19 +68,20 @@ def faraday(options = {})
         authorization = expected_headers_without_authorization.delete('authorization')
         expect(env.request_headers).to include expected_headers_without_authorization
         expect(env.request_headers.fetch('authorization')).to match Regexp.new(authorization)
-        [200, {'Content-Type' => 'application/json'}, JSON.dump(response)]
+        [200, { 'Content-Type' => 'application/json' }, JSON.dump(response)]
       end
     end
   end
 
   context 'without query' do
     let(:signature) do
-      '(' + %w(
+      "(#{%w[
         4029fcbe5aae50c588651d5a587f4a9fd2b7ba25bc03e1ce57432c758d1a7816
         024535e1dd5a9f9eb5a8d2eb99c64678766ad6059bdd51ad85d282f49bd20700
         f15f7c05bba9addb232e39282ea70a7a7c7f2c52dffd4aafe6cc8226fb82d5ab
         f4299dc8cdf28ee680bb882712daf8fac89c1bcfd46f28549bd37b9412d18b72
-      ).join('|') + ')'
+        afb745a953d7e80be81d81ed5425a0a7340cea4d8baf42470bd2c0cda14e5103
+      ].join('|')})"
     end
 
     subject { client.get('/account').body }
@@ -92,29 +93,31 @@ def faraday(options = {})
 
     context 'include space' do
       let(:signature) do
-        '(' + %w(
+        "(#{%w[
           75bb1b4dbbf7b7a502ecb574abfcc2e12ce115da07f876d3b66fd3ff0ad427fd
           f0a9030e2e15012d61af8b708ad358c9a5e5495984162884abf1cb910275223b
           b13ce117f8258ebc4c157b1d216517f38476d80d6a60ace9374d0ec8d500134d
           53df7eeeaec828ce3c8ca011ee35f20ab620fe1d8610ff00e6a57cab642d2436
-        ).join('|') + ')'
+          51e82ebaf936d6dc7a673723240a954b35ac5992e7da3408e25d14715fe24aca
+        ].join('|')})"
       end
 
-      let(:params) { {foo: 'b a r', zoo: 'b a z'} }
+      let(:params) { { foo: 'b a r', zoo: 'b a z' } }
       it { is_expected.to eq response }
     end
 
     context 'not include space' do
       let(:signature) do
-        '(' + %w(
+        "(#{%w[
           94e01cc599b3eef64cc9e08c5f079b0345d5b9dd95cc14d0ea66fc0c5923bf30
           8c58f5f0decfb7f185d290bae83dac382328ba19c862861fd646089ba0083569
           115cea2f319d5cf12bd4fa35b8861eaded8037dad4ccc7e8c8929d150ddf3d66
           552a531f290603c378a4d01a2a307ba4b356c7e7364ac03b337e80085733b61e
-        ).join('|') + ')'
+          3d61f6bd2c027925d3da79c87a69b5b77b595687a5c06576c2d8ff66db459415
+        ].join('|')})"
       end
 
-      let(:params) { {foo: 'bar', zoo: 'baz'} }
+      let(:params) { { foo: 'bar', zoo: 'baz' } }
       it { is_expected.to eq response }
     end
   end
diff --git a/spec/faraday_middleware/aws_sigv4_util_spec.rb b/spec/faraday_middleware/aws_sigv4_util_spec.rb
index 39b50f4..1207d70 100644
--- a/spec/faraday_middleware/aws_sigv4_util_spec.rb
+++ b/spec/faraday_middleware/aws_sigv4_util_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 RSpec.describe FaradayMiddleware::AwsSigV4Util do
   let(:class_with_util) do
     Class.new do
@@ -29,20 +31,20 @@
 
   describe '#seahorse_encode_www_form' do
     subject do
-      class_with_util.new.seahorse_encode_www_form(params).split(?&)
+      class_with_util.new.seahorse_encode_www_form(params).split('&')
     end
 
     context 'not include space' do
       let(:params) do
         [
-          ['foo', 'bar'],
-          ['bar', ['zoo', 'baz']],
+          %w[foo bar],
+          ['bar', %w[zoo baz]],
           ['baz', nil],
-          ['zoo', [nil, 'baz']],
+          ['zoo', [nil, 'baz']]
         ]
       end
 
-      it { is_expected.to match_array URI.encode_www_form(params).split(?&) }
+      it { is_expected.to match_array URI.encode_www_form(params).split('&') }
     end
 
     context 'include space' do
@@ -51,11 +53,11 @@
           ['foo', 'b a r'],
           ['bar', ['z o o', 'baz']],
           ['baz', nil],
-          ['zoo', [nil, 'baz']],
+          ['zoo', [nil, 'baz']]
         ]
       end
 
-      it { is_expected.to match_array URI.encode_www_form(params).gsub(?+, '%20').split(?&) }
+      it { is_expected.to match_array URI.encode_www_form(params).gsub('+', '%20').split('&') }
     end
   end
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 8ce5755..b30be3f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'faraday_middleware'
 require 'faraday_middleware/aws_sigv4'
 require 'net/http'