diff --git a/.github/workflows/depup.yml b/.github/workflows/depup.yml
index 82d060b..0760d6a 100644
--- a/.github/workflows/depup.yml
+++ b/.github/workflows/depup.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: haya14busa/action-depup@v1
         id: depup
         with:
-          file: Dockerfile
+          file: action.yml
           version_name: REVIEWDOG_VERSION
           repo: reviewdog/reviewdog
 
@@ -33,4 +33,4 @@ jobs:
             This PR is auto generated by [depup workflow](https://github.com/${{ github.repository }}/actions?query=workflow%3Adepup).
           branch: depup/reviewdog
           base: master
-          labels: "bump:minor"
\ No newline at end of file
+          labels: "bump:minor"
diff --git a/.github/workflows/dockerimage.yml b/.github/workflows/dockerimage.yml
deleted file mode 100644
index e70018a..0000000
--- a/.github/workflows/dockerimage.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-name: Docker Image CI
-
-on:
-  push:
-    branches:
-      - master
-  pull_request:
-
-jobs:
-
-  build:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Clone repo
-      uses: actions/checkout@master
-
-    - name: Build the Docker image
-      run: docker build . --file Dockerfile --tag $( echo ${{ github.repository }} | tr '[:upper:]' '[:lower:]' ):$(date +%s)
diff --git a/.github/workflows/reviewdog.yml b/.github/workflows/lint.yml
similarity index 56%
rename from .github/workflows/reviewdog.yml
rename to .github/workflows/lint.yml
index 84e523f..6c91c99 100644
--- a/.github/workflows/reviewdog.yml
+++ b/.github/workflows/lint.yml
@@ -1,4 +1,4 @@
-name: reviewdog
+name: Lint
 
 on:
   push:
@@ -7,8 +7,7 @@ on:
   pull_request:
 
 jobs:
-  shellcheck:
-    name: runner / shellcheck
+  Shellcheck:
     runs-on: ubuntu-latest
 
     steps:
@@ -27,28 +26,7 @@ jobs:
           reporter: ${{ steps.reporter.outputs.value }}
           level: warning
 
-  hadolint:
-    name: runner / hadolint
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v2
-
-      - uses: haya14busa/action-cond@v1
-        id: reporter
-        with:
-          cond: ${{ github.event_name == 'pull_request' }}
-          if_true: "github-pr-review"
-          if_false: "github-check"
-
-      - uses: reviewdog/action-hadolint@v1
-        with:
-          github_token: ${{ secrets.github_token }}
-          reporter: ${{ steps.reporter.outputs.value }}
-          level: warning
-
-  misspell:
-    name: runner / misspell
+  Misspell:
     runs-on: ubuntu-latest
 
     steps:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 187dddb..fad9413 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -10,7 +10,7 @@ on:
 jobs:
   release:
     runs-on: ubuntu-latest
-    
+
     steps:
       - uses: actions/checkout@v2
 
diff --git a/.github/workflows/test.yml b/.github/workflows/tests.yml
similarity index 64%
rename from .github/workflows/test.yml
rename to .github/workflows/tests.yml
index 9151147..9864e56 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/tests.yml
@@ -1,4 +1,4 @@
-name: Test
+name: Tests
 
 on:
   push:
@@ -6,9 +6,13 @@ on:
       - master
   pull_request:
 
+defaults:
+  run:
+    shell: bash
+
 jobs:
   test-check:
-    name: runner / tfsec (github-check)
+    name: tfsec (github-check)
     runs-on: ubuntu-latest
 
     steps:
@@ -30,14 +34,14 @@ jobs:
           tfsec_return="${{ steps.test.outputs.tfsec-return-code }}"
           reviewdog_return="${{ steps.test.outputs.reviewdog-return-code }}"
 
-          if [ "$tfsec_return" -eq 1 ]; then
+          if [[ "$tfsec_return" -eq 1 ]]; then
             echo "tfsec correctly returned failure ${tfsec_return}"
           else
             echo "tfsec returned ${tfsec_return}, expected '1'. Failing..."
             exit 1
           fi
 
-          if [ "$reviewdog_return" -eq 0 ]; then
+          if [[ "$reviewdog_return" -eq 0 ]]; then
             echo "reviewdog correctly returned success: ${reviewdog_return}"
           else
             echo "reviewdog returned ${reviewdog_return}, expected '0'. Failing..."
@@ -46,7 +50,7 @@ jobs:
 
   test-pr-check:
     if: github.event_name == 'pull_request'
-    name: runner / tfsec (github-pr-check)
+    name: tfsec (github-pr-check)
     runs-on: ubuntu-latest
 
     steps:
@@ -68,14 +72,14 @@ jobs:
           tfsec_return="${{ steps.test.outputs.tfsec-return-code }}"
           reviewdog_return="${{ steps.test.outputs.reviewdog-return-code }}"
 
-          if [ "$tfsec_return" -eq 1 ]; then
+          if [[ "$tfsec_return" -eq 1 ]]; then
             echo "tfsec correctly returned failure ${tfsec_return}"
           else
             echo "tfsec returned ${tfsec_return}, expected '1'. Failing..."
             exit 1
           fi
 
-          if [ "$reviewdog_return" -eq 0 ]; then
+          if [[ "$reviewdog_return" -eq 0 ]]; then
             echo "reviewdog correctly returned success: ${reviewdog_return}"
           else
             echo "reviewdog returned ${reviewdog_return}, expected '0'. Failing..."
@@ -84,7 +88,7 @@ jobs:
 
   test-pr-review:
     if: github.event_name == 'pull_request'
-    name: runner / tfsec (github-pr-review)
+    name: tfsec (github-pr-review)
     runs-on: ubuntu-latest
 
     steps:
@@ -108,15 +112,55 @@ jobs:
           tfsec_return="${{ steps.test.outputs.tfsec-return-code }}"
           reviewdog_return="${{ steps.test.outputs.reviewdog-return-code }}"
 
-          if [ "$tfsec_return" -eq 1 ]; then
+          if [[ "$tfsec_return" -eq 1 ]]; then
+            echo "tfsec correctly returned failure ${tfsec_return}"
+          else
+            echo "tfsec returned ${tfsec_return}, expected '1'. Failing..."
+            exit 1
+          fi
+
+          if [[ "$reviewdog_return" -eq 0 ]]; then
+            echo "reviewdog correctly returned success: ${reviewdog_return}"
+          else
+            echo "reviewdog returned ${reviewdog_return}, expected '0'. Failing..."
+            exit 1
+          fi
+
+  test-operating-systems:
+    strategy:
+       matrix:
+         platform: [ubuntu-latest, macos-latest, windows-latest]
+    name: tfsec (${{ matrix.platform }})
+    runs-on: ${{ matrix.platform }}
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: ./
+        continue-on-error: true
+        id: test
+        with:
+          github_token: ${{ secrets.github_token }}
+          reporter: github-check
+          level: info
+          working_directory: testdata
+
+      # The check is expected to fail on the test data
+      - name: Check return codes
+        if: success() || failure ()
+        run: |
+          tfsec_return="${{ steps.test.outputs.tfsec-return-code }}"
+          reviewdog_return="${{ steps.test.outputs.reviewdog-return-code }}"
+
+          if [[ "$tfsec_return" -eq 1 ]]; then
             echo "tfsec correctly returned failure ${tfsec_return}"
           else
             echo "tfsec returned ${tfsec_return}, expected '1'. Failing..."
             exit 1
           fi
 
-          if [ "$reviewdog_return" -eq 0 ]; then
-            echo "reviewdog correctly returned failure: ${reviewdog_return}"
+          if [[ "$reviewdog_return" -eq 0 ]]; then
+            echo "reviewdog correctly returned success: ${reviewdog_return}"
           else
             echo "reviewdog returned ${reviewdog_return}, expected '0'. Failing..."
             exit 1
diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index b0cbaab..0000000
--- a/Dockerfile
+++ /dev/null
@@ -1,18 +0,0 @@
-FROM alpine:3.13
-
-ENV REVIEWDOG_VERSION=v0.11.0
-
-# hadolint ignore=DL3018
-RUN apk --no-cache --update add bash git \
-    && rm -rf /var/cache/apk/*
-
-SHELL ["/bin/bash", "-eo", "pipefail", "-c"]
-
-RUN wget -O - -q https://raw.githubusercontent.com/reviewdog/reviewdog/master/install.sh | sh -s -- -b /usr/local/bin/
-
-RUN wget -O - -q "$(wget -q https://api.github.com/repos/liamg/tfsec/releases/latest -O - | grep -o -E "https://.+?tfsec-linux-amd64")" > tfsec \
-    && install tfsec /usr/local/bin/
-
-COPY entrypoint.sh /entrypoint.sh
-
-ENTRYPOINT ["/entrypoint.sh"]
diff --git a/README.md b/README.md
index 3974e95..51597c2 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # GitHub Action: Run tfsec with reviewdog
 
-[![Test](https://github.com/reviewdog/action-tfsec/workflows/Test/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%3ATest)
-[![reviewdog](https://github.com/reviewdog/action-tfsec/workflows/reviewdog/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%3Areviewdog)
+[![Tests](https://github.com/reviewdog/action-tfsec/workflows/Tests/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%3ATests)
+[![Lint](https://github.com/reviewdog/action-tfsec/workflows/Lint/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%Lint)
 [![depup](https://github.com/reviewdog/action-tfsec/workflows/depup/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%3Adepup)
 [![release](https://github.com/reviewdog/action-tfsec/workflows/release/badge.svg)](https://github.com/reviewdog/action-tfsec/actions?query=workflow%3Arelease)
 [![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/reviewdog/action-tfsec?logo=github&sort=semver)](https://github.com/reviewdog/action-tfsec/releases)
@@ -33,6 +33,11 @@ the Pull Request Conversation:
 
 **Required**. Must be in form of `github_token: ${{ secrets.github_token }}`.
 
+### `working_directory`
+
+Optional. Directory to run the action on, from the repo root.
+The default is `.` ( root of the repository).
+
 ### `level`
 
 Optional. Report level for reviewdog [`info`,`warning`,`error`].
@@ -50,7 +55,7 @@ Optional. Filtering for the reviewdog command [`added`,`diff_context`,`file`,`no
 
 The default is `added`.
 
-See [reviewdog doccumentation for filter mode](https://github.com/reviewdog/reviewdog/tree/master#filter-mode) for details.
+See [reviewdog documentation for filter mode](https://github.com/reviewdog/reviewdog/tree/master#filter-mode) for details.
 
 ### `fail_on_error`
 
@@ -58,14 +63,14 @@ Optional. Exit code for reviewdog when errors are found [`true`,`false`].
 
 The default is `false`.
 
-See [reviewdog doccumentation for exit codes](https://github.com/reviewdog/reviewdog/tree/master#exit-codes) for details.
+See [reviewdog documentation for exit codes](https://github.com/reviewdog/reviewdog/tree/master#exit-codes) for details.
 
-### `working_directory`
+### `flags`
 
-Optional. Directory to run the action on, from the repo root.
-The default is `.` ( root of the repository).
+Optional. Additional reviewdog flags. Useful for debugging errors, when it can be set to `-tee`.
+The default is ``.
 
-### `flags`
+### `tfsec_flags`
 
 Optional. List of arguments to send to tfsec.
 For the output to be parsable by reviewdog [`--format=checkstyle` is enforced](./entrypoint.sh).
@@ -89,21 +94,23 @@ on: [pull_request]
 jobs:
   tfsec:
     name: runner / tfsec
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest # Windows and macOS are also supported
 
     steps:
       - name: Clone repo
-        uses: actions/checkout@master
+        uses: actions/checkout@v2
 
-      - name: tfsec
+      - name: Run tfsec with reviewdog output on the PR
         uses: reviewdog/action-tfsec@master
         with:
           github_token: ${{ secrets.github_token }}
-          working_directory: "testdata" # Change working directory
-          reporter: github-pr-review # Change reporter
-          fail_on_error: "true" # Fail action if errors are found
-          filter_mode: "nofilter" # Check all files, not just the diff
-          flags: "" # Optional
+          working_directory: my_directory # Change working directory
+          level: info # Get more output from reviewdog
+          reporter: github-pr-review # Change reviewdog reporter
+          filter_mode: nofilter # Check all files, not just the diff
+          fail_on_error: true # Fail action if errors are found
+          flags: -tee # Add debug flag to reviewdog
+          tfsec_flags: "" # Optional
 ```
 
 ## Development
@@ -111,13 +118,14 @@ jobs:
 ### Release
 
 #### [haya14busa/action-bumpr](https://github.com/haya14busa/action-bumpr)
+
 You can bump version on merging Pull Requests with specific labels (bump:major,bump:minor,bump:patch).
 Pushing tag manually by yourself also work.
 
 #### [haya14busa/action-update-semver](https://github.com/haya14busa/action-update-semver)
 
 This action updates major/minor release tags on a tag push. e.g. Update v1 and v1.2 tag when released v1.2.3.
-ref: https://help.github.com/en/articles/about-actions#versioning-your-action
+ref: <https://help.github.com/en/articles/about-actions#versioning-your-action>
 
 ### Lint - reviewdog integration
 
@@ -131,5 +139,6 @@ Supported linters:
 - [reviewdog/action-misspell](https://github.com/reviewdog/action-misspell)
 
 ### Dependencies Update Automation
+
 This repository uses [haya14busa/action-depup](https://github.com/haya14busa/action-depup) to update
 reviewdog version.
diff --git a/action.yml b/action.yml
index a8d2b25..f60db59 100644
--- a/action.yml
+++ b/action.yml
@@ -6,45 +6,75 @@ inputs:
   github_token:
     description: 'GITHUB_TOKEN'
     required: true
+  working_directory:
+    description: |
+      Directory to run the action on, from the repo root.
+      Default is . ( root of the repository)
+    default: '.'
+    required: false
   level:
     description: 'Report level for reviewdog [info,warning,error]'
     default: 'error'
+    required: false
   reporter:
     description: |
       Reporter of reviewdog command [github-pr-check,github-pr-review].
       Default is github-pr-check.
     default: 'github-pr-check'
+    required: false
   filter_mode:
     description: |
       Filtering for the reviewdog command [added,diff_context,file,nofilter].
       Default is added.
     default: 'added'
+    required: false
   fail_on_error:
     description: |
       Exit code for reviewdog when errors are found [true,false]
       Default is `false`.
     default: 'false'
-  working_directory:
-    description: |
-      Directory to run the action on, from the repo root.
-      Default is . ( root of the repository)
-    default: '.'
+    required: false
   flags:
+    description: 'Additional reviewdog flags'
+    default: ''
+    required: false
+  tfsec_flags:
     description: |
       List of arguments to send to tfsec
       For the output to be parsable by reviewdog --format=checkstyle is enforced
       Default is blank.
     default: ''
+    required: false
 
 outputs:
   tfsec-return-code:
     description: 'tfsec command return code'
+    value: ${{ steps.tfsec.outputs.tfsec-return-code }}
   reviewdog-return-code:
     description: 'reviewdog command return code'
+    value: ${{ steps.tfsec.outputs.reviewdog-return-code }}
 
 runs:
-  using: 'docker'
-  image: 'Dockerfile'
+  using: 'composite'
+  steps:
+    - run: $GITHUB_ACTION_PATH/script.sh
+      id: tfsec
+      shell: bash
+      env:
+        # We may want to allow specifying reviewdog version as
+        # action's input, but let's start with hard coded latest stable version for reviewdog
+        REVIEWDOG_VERSION: v0.11.0
+        # INPUT_<VARIABLE_NAME> is not available in Composite run steps
+        # https://github.community/t/input-variable-name-is-not-available-in-composite-run-steps/127611
+        INPUT_GITHUB_TOKEN: ${{ inputs.github_token }}
+        INPUT_WORKING_DIRECTORY: ${{ inputs.working_directory }}
+        INPUT_LEVEL: ${{ inputs.level }}
+        INPUT_REPORTER: ${{ inputs.reporter }}
+        INPUT_FILTER_MODE: ${{ inputs.filter_mode }}
+        INPUT_FAIL_ON_ERROR: ${{ inputs.fail_on_error }}
+        INPUT_FLAGS: ${{ inputs.flags }}
+        INPUT_TFSEC_FLAGS: ${{ inputs.tfsec_flags }}
+
 branding:
   icon: 'edit'
   color: 'gray-dark'
diff --git a/entrypoint.sh b/entrypoint.sh
deleted file mode 100755
index 20d4ba8..0000000
--- a/entrypoint.sh
+++ /dev/null
@@ -1,17 +0,0 @@
-#!/bin/bash
-
-if [ -n "${GITHUB_WORKSPACE}" ]; then
-  cd "${GITHUB_WORKSPACE}" || exit
-fi
-
-export REVIEWDOG_GITHUB_API_TOKEN="${INPUT_GITHUB_TOKEN}"
-
-tfsec --format=checkstyle ${INPUT_FLAGS} "${INPUT_WORKING_DIRECTORY}" \
-  | reviewdog -f=checkstyle -name="tfsec" -reporter="${INPUT_REPORTER}" -level="${INPUT_LEVEL}" -fail-on-error="${INPUT_FAIL_ON_ERROR}" -filter-mode="${INPUT_FILTER_MODE}"
-
-tfsec_return="${PIPESTATUS[0]}" reviewdog_return="${PIPESTATUS[1]}" exit_code=$?
-
-echo ::set-output name=tfsec-return-code::"${tfsec_return}"
-echo ::set-output name=reviewdog-return-code::"${reviewdog_return}"
-
-exit $exit_code
diff --git a/script.sh b/script.sh
new file mode 100755
index 0000000..c23fa06
--- /dev/null
+++ b/script.sh
@@ -0,0 +1,76 @@
+#!/bin/bash
+
+# Fail fast on errors, unset variables, and failures in piped commands
+set -Eeuo pipefail
+
+cd "${GITHUB_WORKSPACE}/${INPUT_WORKING_DIRECTORY}" || exit
+
+echo '::group::Preparing ...'
+  unameOS="$(uname -s)"
+  case "${unameOS}" in
+    Linux*)     os=linux;;
+    Darwin*)    os=darwin;;
+    CYGWIN*)    os=windows;;
+    MINGW*)     os=windows;;
+    MSYS_NT*)   os=windows;;
+    *)          echo "Unknown system: ${unameOS}" && exit 1
+  esac
+
+  unameArch="$(uname -m)"
+  case "${unameArch}" in
+    x86*)      arch=amd64;;
+    *)         echo "Unsupported architecture: ${unameArch}. Only AMD64 is supported by tfsec" && exit 1
+    esac
+
+  TEMP_PATH="$(mktemp -d)"
+  echo "Detected ${os} running on ${arch}, will install tools in ${TEMP_PATH}"
+  REVIEWDOG_PATH="${TEMP_PATH}/reviewdog"
+  TFSEC_PATH="${TEMP_PATH}/tfsec"
+echo '::endgroup::'
+
+echo "::group::🐶 Installing reviewdog (${REVIEWDOG_VERSION}) ... https://github.com/reviewdog/reviewdog"
+  curl -sfL https://raw.githubusercontent.com/reviewdog/reviewdog/master/install.sh | sh -s -- -b "${REVIEWDOG_PATH}" "${REVIEWDOG_VERSION}" 2>&1
+echo '::endgroup::'
+
+echo '::group:: Installing tfsec (latest) ... https://github.com/tfsec/tfsec'
+  test ! -d "${TFSEC_PATH}" && install -d "${TFSEC_PATH}"
+
+  binary="tfsec"
+  url="https://github.com/tfsec/tfsec/releases/latest/download/tfsec-${os}-${arch}"
+  if [[ "${os}" = "windows" ]]; then
+    url+=".exe"
+    binary+=".exe"
+  fi
+
+  curl --silent --show-error --fail \
+    --location "${url}" \
+    --output "${binary}"
+  install tfsec "${TFSEC_PATH}"
+echo '::endgroup::'
+
+echo "::group:: Print tfsec details ..."
+  "${TFSEC_PATH}/tfsec" --version
+echo '::endgroup::'
+
+echo '::group:: Running tfsec with reviewdog 🐶 ...'
+  export REVIEWDOG_GITHUB_API_TOKEN="${INPUT_GITHUB_TOKEN}"
+
+  # Allow failures now, as reviewdog handles them
+  set +Eeuo pipefail
+
+  # shellcheck disable=SC2086
+  "${TFSEC_PATH}/tfsec" --format=checkstyle ${INPUT_TFSEC_FLAGS:-} . \
+    | "${REVIEWDOG_PATH}/reviewdog" -f=checkstyle \
+        -name="tfsec" \
+        -reporter="${INPUT_REPORTER}" \
+        -level="${INPUT_LEVEL}" \
+        -fail-on-error="${INPUT_FAIL_ON_ERROR}" \
+        -filter-mode="${INPUT_FILTER_MODE}" \
+        ${INPUT_FLAGS}
+
+  tfsec_return="${PIPESTATUS[0]}" reviewdog_return="${PIPESTATUS[1]}" exit_code=$?
+  echo "::set-output name=tfsec-return-code::${tfsec_return}"
+  echo "::set-output name=reviewdog-return-code::${reviewdog_return}"
+echo '::endgroup::'
+
+exit "${exit_code}"
diff --git a/testdata/example.tf b/testdata/example.tf
index b1cef17..660b51b 100644
--- a/testdata/example.tf
+++ b/testdata/example.tf
@@ -1,19 +1,45 @@
-resource "aws_security_group_rule" "my-rule" {
-    type        = "ingress"
-    cidr_blocks = ["0.0.0.0/0"]
+resource "aws_vpc" "main" {
+  cidr_block = "10.0.0.0/16"
 }
 
-resource "aws_alb_listener" "my-alb-listener"{
-    port     = "80"
-    protocol = "HTTP"
+resource "aws_security_group" "example" {
+  name        = "example"
+  description = "Very complex Security Group for testing"
+  vpc_id      = aws_vpc.main.id
+
+  tags = {
+    "Name" = "example"
+  }
+}
+
+resource "aws_security_group_rule" "example_rule" {
+  security_group_id = aws_security_group.example.id
+  description       = "Allow all traffic from Internet which will make tfsec throw an error"
+
+  type      = "ingress"
+  from_port = "0"
+  to_port   = "65535"
+  protocol  = "tcp"
+
+  cidr_blocks      = ["0.0.0.0/0"]
+  ipv6_cidr_blocks = ["::/0"]
 }
 
-resource "aws_db_security_group" "my-group" {
 
+resource "azurerm_resource_group" "example" {
+  name     = "example-resources"
+  location = "West Europe"
 }
 
-resource "azurerm_managed_disk" "source" {
-    encryption_settings {
-        enabled = false
-    }
+resource "azurerm_managed_disk" "example" {
+  name                 = "acctestmd"
+  location             = "West Europe"
+  resource_group_name  = azurerm_resource_group.example.name
+  storage_account_type = "Standard_LRS"
+  create_option        = "Empty"
+  disk_size_gb         = "1"
+
+  encryption_settings {
+    enabled = false
+  }
 }
diff --git a/testdata/main.tf b/testdata/main.tf
new file mode 100644
index 0000000..ae2eece
--- /dev/null
+++ b/testdata/main.tf
@@ -0,0 +1,23 @@
+terraform {
+  required_version = "~> 0.15"
+
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = "~> 3"
+    }
+
+    azurerm = {
+      source  = "hashicorp/azurerm"
+      version = "~> 2"
+    }
+  }
+}
+
+provider "aws" {
+  region = "eu-west-1"
+}
+
+provider "azurerm" {
+  features {}
+}