diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..4eed74e
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,10 @@
+# Set the default behavior, in case people don't have core.autocrlf set.
+* text eol=lf
+/.gitattributes export-ignore
+/.gitignore export-ignore
+/.github export-ignore
+/phpcs.xml.dist export-ignore
+/phpstan.neon.dist export-ignore
+/phpunit.xml.dist export-ignore
+/psalm.xml.dist export-ignore
+/tests export-ignore
diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
new file mode 100644
index 0000000..2582648
--- /dev/null
+++ b/.github/workflows/coding-standards.yml
@@ -0,0 +1,34 @@
+name: "Coding Standards"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+
+jobs:
+  coding-standards:
+    name: "Coding Standards"
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "${{ matrix.php-version }}"
+          tools: "cs2pr"
+
+      - name: "Install dependencies with Composer"
+        uses: "ramsey/composer-install@v1"
+
+      - name: "Run PHP_CodeSniffer"
+        run: "vendor/bin/phpcs -q --no-colors --report=checkstyle | cs2pr"
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
new file mode 100644
index 0000000..7131de5
--- /dev/null
+++ b/.github/workflows/continuous-integration.yml
@@ -0,0 +1,74 @@
+name: "CI"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+  schedule:
+    - cron: "42 3 * * *"
+
+jobs:
+  phpunit:
+    name: "PHPUnit"
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+          - "8.0"
+        dependencies:
+          - "highest"
+        include:
+          - dependencies: "lowest"
+            php-version: "7.4"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+        with:
+          fetch-depth: 2
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          php-version: "${{ matrix.php-version }}"
+          coverage: "pcov"
+          ini-values: "zend.assertions=1"
+
+      - name: "Install dependencies with Composer"
+        uses: "ramsey/composer-install@v1"
+        with:
+          dependency-versions: "${{ matrix.dependencies }}"
+
+      - name: "Run PHPUnit"
+        run: "vendor/bin/phpunit --coverage-clover=coverage.xml"
+
+      - name: "Upload coverage file"
+        uses: "actions/upload-artifact@v2"
+        with:
+          name: "phpunit-${{ matrix.deps }}-${{ matrix.php-version }}.coverage"
+          path: "coverage.xml"
+
+  upload_coverage:
+    name: "Upload coverage to Codecov"
+    runs-on: "ubuntu-20.04"
+    needs:
+      - "phpunit"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+        with:
+          fetch-depth: 2
+
+      - name: "Download coverage files"
+        uses: "actions/download-artifact@v2"
+        with:
+          path: "reports"
+
+      - name: "Upload to Codecov"
+        uses: "codecov/codecov-action@v1"
+        with:
+          directory: reports
diff --git a/.github/workflows/static-analysis.yml b/.github/workflows/static-analysis.yml
new file mode 100644
index 0000000..62fd758
--- /dev/null
+++ b/.github/workflows/static-analysis.yml
@@ -0,0 +1,59 @@
+name: "Static Analysis"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+
+jobs:
+  static-analysis-phpstan:
+    name: "Static Analysis with PHPStan"
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+
+    steps:
+      - name: "Checkout code"
+        uses: "actions/checkout@v2"
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "${{ matrix.php-version }}"
+          tools: "cs2pr"
+
+      - name: "Install dependencies with Composer"
+        uses: "ramsey/composer-install@v1"
+
+      - name: "Run a static analysis with phpstan/phpstan"
+        run: "vendor/bin/phpstan --error-format=checkstyle | cs2pr"
+
+  static-analysis-psalm:
+    name: "Static Analysis with Psalm"
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Psalm
+        uses: docker://vimeo/psalm-github-actions:4.3.2
+        with:
+          args: --shepherd
+          composer_require_dev: true
+          security_analysis: true
+          report_file: results.sarif
+      - name: Upload Security Analysis results to GitHub
+        uses: github/codeql-action/upload-sarif@v1
+        with:
+          sarif_file: results.sarif
diff --git a/.gitignore b/.gitignore
index 202d7c9..56ed85a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,7 +1,8 @@
-/vendor/
 /.phpcs-cache
 /.phpunit.result.cache
 /composer.lock
 /phpcs.xml
 /phpstan.neon
+/psalm.xml
 /phpunit.xml
+/vendor/
diff --git a/.scrutinizer.yml b/.scrutinizer.yml
deleted file mode 100644
index 96b33ae..0000000
--- a/.scrutinizer.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-build:
-    nodes:
-        analysis:
-            environment:
-                php:
-                    version: 7.2
-            cache:
-                disabled: false
-                directories:
-                    - ~/.composer/cache
-            project_setup:
-                override: true
-            tests:
-                override:
-                    - php-scrutinizer-run
-                    - phpcs-run
-    dependencies:
-        override:
-            - COMPOSER_ARGS="--prefer-stable" make
-
-checks:
-    php:
-        code_rating: true
-
-tools:
-    external_code_coverage:
-        timeout: 3600
-
-build_failure_conditions:
-    - 'elements.rating(<= C).new.exists'                        # No new classes/methods with a rating of C or worse allowed
-    - 'issues.severity(>= MAJOR).new.exists'                    # New issues of major or higher severity
-    - 'project.metric_change("scrutinizer.test_coverage", < 0)' # Code Coverage decreased from previous inspection
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index ed38a5f..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,56 +0,0 @@
-dist: xenial
-language: php
-
-php:
-    - "7.2"
-    - "7.3"
-    - 7.4snapshot
-    - nightly
-
-env:
-    - DEPENDENCIES=
-    - DEPENDENCIES=--prefer-lowest
-
-before_install:
-    - mv ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/xdebug.ini{,.disabled} || echo "xdebug not available"
-
-install: COMPOSER_ARGS="--prefer-stable $DEPENDENCIES" make
-
-script: make test
-
-stages:
-    - Code Quality
-    - Test
-
-jobs:
-    allow_failures:
-        -   php: 7.4snapshot
-        -   php: nightly
-
-    include:
-        -   stage: Code Quality
-            name: Lint
-            php: "7.2"
-            script: make lint
-        -   name: Coding Standard
-            php: "7.2"
-            script: make cs
-        -   name: Static Analysis
-            php: "7.2"
-            script: make static-analysis
-
-        -   stage: Test
-            name: COVERAGE
-            php: "7.2"
-            before_script:
-                - mv ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/xdebug.ini{.disabled,}
-                - if [[ ! $(php -m | grep -si xdebug) ]]; then echo "xdebug required for coverage"; exit 1; fi
-            script:
-                - ./vendor/bin/phpunit --coverage-clover ./build/logs/clover.xml
-            after_script:
-                - wget https://github.com/scrutinizer-ci/ocular/releases/download/1.6.0/ocular.phar
-                - php ocular.phar code-coverage:upload --format=php-clover build/logs/clover.xml
-
-cache:
-    directories:
-        - $HOME/.composer/cache
diff --git a/LICENCE b/LICENCE
new file mode 100644
index 0000000..6d861d3
--- /dev/null
+++ b/LICENCE
@@ -0,0 +1,30 @@
+License
+=======
+
+This work is published under the MIT license (see full statement below).
+If you want to deal (as described below) only with a part of this work,
+you have to include this license in the part itself.
+
+The MIT License (MIT)
+---------------------
+
+Copyright (c) 2014-2015 Vašek Purchart
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
diff --git a/README.md b/README.md
index 6e391e5..cfebd40 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,38 @@
 # JSON RPC 2.0 PSR-7 Message Factory
 
-[![Build Status](https://travis-ci.com/simpod/json-rpc.svg?branch=master)](https://travis-ci.com/simpod/json-rpc)
-[![Downloads](https://poser.pugx.org/simpod/json-rpc/d/total.svg)](https://packagist.org/packages/simpod/json-rpc)
-[![Packagist](https://poser.pugx.org/simpod/json-rpc/v/stable.svg)](https://packagist.org/packages/simpod/json-rpc)
-[![Licence](https://poser.pugx.org/simpod/json-rpc/license.svg)](https://packagist.org/packages/simpod/json-rpc)
-[![Quality Score](https://scrutinizer-ci.com/g/simpod/json-rpc/badges/quality-score.png?b=master)](https://scrutinizer-ci.com/g/simpod/json-rpc)
-[![Code Coverage](https://scrutinizer-ci.com/g/simpod/json-rpc/badges/coverage.png?b=master)](https://scrutinizer-ci.com/g/simpod/json-rpc)
+[![GitHub Actions][GA Image]][GA Link]
+[![Shepherd Type][Shepherd Image]][Shepherd Link]
+[![Code Coverage][Coverage Image]][CodeCov Link]
+[![Downloads][Downloads Image]][Packagist Link]
+[![Packagist][Packagist Image]][Packagist Link]
+[![Infection MSI][Infection Image]][Infection Link]
+
+## Installation
+
+Add as [Composer](https://getcomposer.org/) dependency:
+
+```sh
+composer require simpod/json-rpc
+```
+
+[GA Image]: https://github.com/simPod/PhpJsonRpc/workflows/CI/badge.svg
+
+[GA Link]: https://github.com/simPod/PhpJsonRpc/actions?query=workflow%3A%22CI%22+branch%3Amaster
+
+[Shepherd Image]: https://shepherd.dev/github/simPod/PhpJsonRpc/coverage.svg
+
+[Shepherd Link]: https://shepherd.dev/github/simPod/PhpJsonRpc
+
+[Coverage Image]: https://codecov.io/gh/simPod/PhpJsonRpc/branch/master/graph/badge.svg
+
+[CodeCov Link]: https://codecov.io/gh/simPod/PhpJsonRpc/branch/master
+
+[Downloads Image]: https://poser.pugx.org/simpod/json-rpc/d/total.svg
+
+[Packagist Image]: https://poser.pugx.org/simpod/json-rpc/v/stable.svg
+
+[Packagist Link]: https://packagist.org/packages/simpod/json-rpc
+
+[Infection Image]: https://badge.stryker-mutator.io/github.com/simPod/PhpJsonRpc/master
+
+[Infection Link]: https://infection.github.io
diff --git a/composer.json b/composer.json
index fdd0691..d7084b4 100644
--- a/composer.json
+++ b/composer.json
@@ -16,7 +16,7 @@
         }
     },
     "require": {
-        "php": "^7.2",
+        "php": "^7.4 || ^8.0",
         "ext-json": "*",
         "nyholm/psr7": "^1.2",
         "php-http/httplug": "^2.0",
@@ -25,14 +25,17 @@
         "thecodingmachine/safe": "^1.0.2"
     },
     "require-dev": {
-        "doctrine/coding-standard": "^6.0",
+        "cdn77/coding-standard": "^4.0",
+        "hectorj/safe-php-psalm-plugin": "dev-master#b60ed45a06d5246e2efd193ce9c8940b244d5c7d",
         "jakub-onderka/php-parallel-lint": "^1.0",
         "phpstan/extension-installer": "^1.0",
-        "phpstan/phpstan": "^0.11.16",
-        "phpstan/phpstan-phpunit": "^0.11.2",
-        "phpstan/phpstan-strict-rules": "^0.11.1",
-        "phpunit/phpunit": "^8.4",
-        "thecodingmachine/phpstan-safe-rule": "^1.0"
+        "phpstan/phpstan": "0.12.81",
+        "phpstan/phpstan-phpunit": "0.12.18",
+        "phpstan/phpstan-strict-rules": "^0.12.7",
+        "phpunit/phpunit": "^9.5",
+        "psalm/plugin-phpunit": "0.15.1",
+        "thecodingmachine/phpstan-safe-rule": "^1.0",
+        "vimeo/psalm": "4.6.3"
     },
     "config": {
         "sort-packages": true
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index e6d6f46..e8ad2a2 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -3,9 +3,11 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="vendor/squizlabs/php_codesniffer/phpcs.xsd"
 >
-    <arg name="cache" value=".phpcs-cache"/>
+    <arg name="cache" value=".phpcs-cache" />
 
-    <rule ref="Doctrine"/>
+    <rule ref="Cdn77">
+        <exclude name="SlevomatCodingStandard.Files.LineLength.LineTooLong" />
+    </rule>
 
     <file>src/</file>
     <file>tests/</file>
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 9e70cb2..8ea502f 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,6 +1,4 @@
 parameters:
-    bootstrap: %currentWorkingDirectory%/tests/bootstrap.php
-    memory-limit: -1
     level: max
     paths:
         - %currentWorkingDirectory%/src
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 9e0190f..9247927 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -13,9 +13,9 @@
             <directory>tests</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist processUncoveredFilesFromWhitelist="true">
+    <coverage>
+        <include>
             <directory suffix=".php">src</directory>
-        </whitelist>
-    </filter>
+        </include>
+    </coverage>
 </phpunit>
diff --git a/psalm.xml.dist b/psalm.xml.dist
new file mode 100644
index 0000000..fe880b6
--- /dev/null
+++ b/psalm.xml.dist
@@ -0,0 +1,25 @@
+<?xml version="1.0"?>
+<psalm
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    ensureArrayStringOffsetsExist="true"
+    errorLevel="1"
+    findUnusedPsalmSuppress="true"
+    findUnusedVariablesAndParams="true"
+    ignoreInternalFunctionFalseReturn="false"
+    ignoreInternalFunctionNullReturn="false"
+    strictBinaryOperands="true"
+>
+    <projectFiles>
+        <directory name="src" />
+        <directory name="tests" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+    <plugins>
+        <pluginClass class="HectorJ\SafePHPPsalmPlugin\Plugin"/>
+        <pluginClass class="Psalm\PhpUnitPlugin\Plugin" />
+    </plugins>
+</psalm>
diff --git a/src/Extractor/Extractor.php b/src/Extractor/Extractor.php
index adccf46..846ccc9 100644
--- a/src/Extractor/Extractor.php
+++ b/src/Extractor/Extractor.php
@@ -5,16 +5,18 @@
 namespace SimPod\JsonRpc\Extractor;
 
 use Psr\Http\Message\MessageInterface;
+
 use function Safe\json_decode;
 
 abstract class Extractor
 {
-    /** @var mixed[] */
-    protected $messageContents;
+    /** @var array{id: string, jsonrpc: string, error?: array{code: int, message: string, data?: mixed}, method: string, params?: array<string, mixed>} */
+    protected array $messageContents;
 
     public function __construct(MessageInterface $message)
     {
-        $body                  = $message->getBody();
-        $this->messageContents = json_decode((string) $body, true);
+        /** @var array{id: string, jsonrpc: string, error?: array{code: int, message: string, data?: mixed}, method: string, params?: array<string, mixed>} $contents */
+        $contents = json_decode((string) $message->getBody(), true);
+        $this->messageContents = $contents;
     }
 }
diff --git a/src/Extractor/RequestExtractor.php b/src/Extractor/RequestExtractor.php
index c15d244..c3fa34c 100644
--- a/src/Extractor/RequestExtractor.php
+++ b/src/Extractor/RequestExtractor.php
@@ -6,9 +6,7 @@
 
 final class RequestExtractor extends Extractor
 {
-    /**
-     * @return string|int|null
-     */
+    /** @return string|int|null */
     public function getId()
     {
         return $this->messageContents['id'] ?? null;
@@ -19,9 +17,7 @@ public function getMethod() : string
         return $this->messageContents['method'];
     }
 
-    /**
-     * @return mixed[]|null
-     */
+    /** @return mixed[]|null */
     public function getParams() : ?array
     {
         return $this->messageContents['params'] ?? null;
diff --git a/src/Extractor/ResponseExtractor.php b/src/Extractor/ResponseExtractor.php
index 4eb97ba..9752f73 100644
--- a/src/Extractor/ResponseExtractor.php
+++ b/src/Extractor/ResponseExtractor.php
@@ -8,33 +8,33 @@ final class ResponseExtractor extends Extractor
 {
     public function getErrorCode() : ?int
     {
-        return $this->messageContents['error']['code'] ?? null;
+        $error = $this->messageContents['error'] ?? null;
+
+        return $error === null ? null : $error['code'];
     }
 
     public function getErrorMessage() : ?string
     {
-        return $this->messageContents['error']['message'] ?? null;
+        $error = $this->messageContents['error'] ?? null;
+
+        return $error === null ? null : $error['message'];
     }
 
-    /**
-     * @return mixed
-     */
+    /** @return mixed */
     public function getErrorData()
     {
-        return $this->messageContents['error']['data'] ?? null;
+        $error = $this->messageContents['error'] ?? null;
+
+        return $error === null ? null : ($error['data'] ?? null);
     }
 
-    /**
-     * @return string|int|null
-     */
+    /** @return string|int|null */
     public function getId()
     {
         return $this->messageContents['id'] ?? null;
     }
 
-    /**
-     * @return mixed
-     */
+    /** @return mixed */
     public function getResult()
     {
         return $this->messageContents['result'] ?? null;
diff --git a/src/HttpJsonRpcRequestFactory.php b/src/HttpJsonRpcRequestFactory.php
index 53cb555..a265703 100644
--- a/src/HttpJsonRpcRequestFactory.php
+++ b/src/HttpJsonRpcRequestFactory.php
@@ -7,14 +7,14 @@
 use Nyholm\Psr7\Stream;
 use Psr\Http\Message\RequestFactoryInterface;
 use Psr\Http\Message\RequestInterface;
+
 use function Safe\json_encode;
 
 final class HttpJsonRpcRequestFactory implements JsonRpcRequestFactory
 {
     private const V2_0 = '2.0';
 
-    /** @var RequestFactoryInterface */
-    private $messageFactory;
+    private RequestFactoryInterface $messageFactory;
 
     public function __construct(RequestFactoryInterface $messageFactory)
     {
@@ -29,8 +29,8 @@ public function notification(string $method, ?array $params = null) : RequestInt
         return $this->createRequest(
             [
                 'jsonrpc' => self::V2_0,
-                'method'  => $method,
-                'params'  => $params,
+                'method' => $method,
+                'params' => $params,
             ]
         );
     }
@@ -42,8 +42,8 @@ public function request($id, string $method, ?array $params = null) : RequestInt
     {
         $body = [
             'jsonrpc' => self::V2_0,
-            'method'  => $method,
-            'id'      => $id,
+            'method' => $method,
+            'id' => $id,
         ];
 
         if ($params !== null) {
@@ -53,9 +53,7 @@ public function request($id, string $method, ?array $params = null) : RequestInt
         return $this->createRequest($body);
     }
 
-    /**
-     * @param mixed[] $body
-     */
+    /** @param mixed[] $body */
     private function createRequest(array $body = []) : RequestInterface
     {
         return $this->messageFactory->createRequest('POST', '')
diff --git a/src/JsonRpcRequestFactory.php b/src/JsonRpcRequestFactory.php
index b6a5d35..50647ca 100644
--- a/src/JsonRpcRequestFactory.php
+++ b/src/JsonRpcRequestFactory.php
@@ -8,7 +8,7 @@
 
 interface JsonRpcRequestFactory
 {
-    public const METHOD_REQUEST      = 'REQUEST';
+    public const METHOD_REQUEST = 'REQUEST';
     public const METHOD_NOTIFICATION = 'NOTIFICATION';
 
     /**