diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index dca4ea9..1da2396 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,10 +32,16 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
+          pip install build
+          pip install flake8
+          pip install pytest
+
+      - name: Build package
+        run: |
+          python -m build
 
       - name: Lint
         run: |
-          pip install flake8
           # stop the build if there are Python syntax errors or undefined names
           flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
           # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
@@ -43,8 +49,6 @@ jobs:
 
       - name: Test
         run: |
-          pip install -e .
-          pip install pytest
           pytest --doctest-modules --doctest-glob='*.rst' --junitxml=junit/test-results-${{ matrix.python-version }}.xml
 
       - name: Upload pytest test results
diff --git a/.gitignore b/.gitignore
index a93118a..913309e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -52,6 +52,7 @@ coverage.xml
 .hypothesis/
 .pytest_cache/
 cover/
+junit/
 
 # Translations
 *.mo
diff --git a/HISTORY.md b/HISTORY.md
index 4f235f5..b1ccc45 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -2,6 +2,13 @@
 
 Nothing yet :)
 
+# 1.0.3
+
+- PR #46 Code optimization for unified diff parsing (Thanks, @babenek)
+- Package using build module and pyproject.toml
+- Support up to 3.11
+- Drop support up to 3.6
+
 # 1.0.2
 
 - Support up to 3.9
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..cd427c0
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,35 @@
+[project]
+name = "whatthepatch"
+version = "1.0.3"
+maintainers = [{ name = "Christopher S. Corley", email = "cscorley@gmail.com" }]
+requires-python = ">=3.7"
+readme = "README.rst"
+description = "A patch parsing and application library."
+keywords = ["patch", "diff", "parser"]
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Intended Audience :: Developers",
+    "Intended Audience :: Science/Research",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.7",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Topic :: Software Development :: Libraries :: Python Modules",
+    "Topic :: Software Development :: Version Control",
+    "Topic :: Software Development",
+    "Topic :: Text Processing",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/cscorley/whatthepatch"
+"Bug Tracker" = "https://github.com/cscorley/whatthepatch/issues"
+
+[build-system]
+requires = ["setuptools>=65.0.0", "wheel"]
+build-backend = "setuptools.build_meta"
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index 2a9acf1..0000000
--- a/setup.cfg
+++ /dev/null
@@ -1,2 +0,0 @@
-[bdist_wheel]
-universal = 1
diff --git a/setup.py b/setup.py
deleted file mode 100644
index 406c1c4..0000000
--- a/setup.py
+++ /dev/null
@@ -1,40 +0,0 @@
-# -*- coding: utf-8 -*-
-
-try:
-    from setuptools import setup
-except ImportError:
-    from distutils.core import setup
-
-
-with open("README.rst") as f:
-    readme = f.read()
-
-setup(
-    name="whatthepatch",
-    version="1.0.2",
-    author="Christopher S. Corley",
-    author_email="cscorley@gmail.com",
-    description="A patch parsing and application library.",
-    long_description=readme,
-    url="https://github.com/cscorley/whatthepatch",
-    license="MIT",
-    packages=["whatthepatch"],
-    include_package_data=True,
-    keywords=["patch", "diff", "parser"],
-    classifiers=[
-        "Operating System :: OS Independent",
-        "License :: OSI Approved :: MIT License",
-        "Development Status :: 5 - Production/Stable",
-        "Intended Audience :: Developers",
-        "Intended Audience :: Science/Research",
-        "Topic :: Software Development",
-        "Topic :: Software Development :: Libraries :: Python Modules",
-        "Topic :: Software Development :: Version Control",
-        "Topic :: Text Processing",
-        "Programming Language :: Python :: 3 :: Only",
-        "Programming Language :: Python :: 3.5",
-        "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
-        "Programming Language :: Python :: 3.8",
-    ],
-)
diff --git a/whatthepatch/__init__.py b/src/whatthepatch/__init__.py
similarity index 100%
rename from whatthepatch/__init__.py
rename to src/whatthepatch/__init__.py
diff --git a/whatthepatch/apply.py b/src/whatthepatch/apply.py
similarity index 97%
rename from whatthepatch/apply.py
rename to src/whatthepatch/apply.py
index 4e05cdd..372548e 100644
--- a/whatthepatch/apply.py
+++ b/src/whatthepatch/apply.py
@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
 
+import os.path
 import subprocess
 import tempfile
-import os.path
 
 from . import patch
-from .exceptions import SubprocessException, HunkApplyException
-from .snippets import which, remove
+from .exceptions import HunkApplyException, SubprocessException
+from .snippets import remove, which
 
 
 def apply_patch(diffs):
diff --git a/whatthepatch/exceptions.py b/src/whatthepatch/exceptions.py
similarity index 100%
rename from whatthepatch/exceptions.py
rename to src/whatthepatch/exceptions.py
diff --git a/whatthepatch/patch.py b/src/whatthepatch/patch.py
similarity index 99%
rename from whatthepatch/patch.py
rename to src/whatthepatch/patch.py
index c928a78..50e0e5c 100644
--- a/whatthepatch/patch.py
+++ b/src/whatthepatch/patch.py
@@ -3,8 +3,8 @@
 import re
 from collections import namedtuple
 
-from .snippets import split_by_regex, findall_regex
 from . import exceptions
+from .snippets import findall_regex, split_by_regex
 
 header = namedtuple(
     "header",
diff --git a/whatthepatch/snippets.py b/src/whatthepatch/snippets.py
similarity index 100%
rename from whatthepatch/snippets.py
rename to src/whatthepatch/snippets.py
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_apply.py b/tests/test_apply.py
index 4a31b7a..ddd7646 100644
--- a/tests/test_apply.py
+++ b/tests/test_apply.py
@@ -1,17 +1,17 @@
 # -*- coding: utf-8 -*-
 
-import whatthepatch as wtp
-from whatthepatch import exceptions
-from whatthepatch.snippets import which
-
-import pytest
 import unittest
 from unittest.case import SkipTest
 
+import pytest
+
+from src.whatthepatch import apply_diff, exceptions, parse_patch
+from src.whatthepatch.snippets import which
+
 
 def _apply(src, diff_text, reverse=False, use_patch=False):
-    diff = next(wtp.parse_patch(diff_text))
-    return wtp.apply.apply_diff(diff, src, reverse, use_patch)
+    diff = next(parse_patch(diff_text))
+    return apply_diff(diff, src, reverse, use_patch)
 
 
 def _apply_r(src, diff_text, reverse=True, use_patch=False):
diff --git a/tests/test_patch.py b/tests/test_patch.py
index 49e72fc..dff1304 100644
--- a/tests/test_patch.py
+++ b/tests/test_patch.py
@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
 
-import whatthepatch as wtp
-from whatthepatch.patch import Change, diffobj, header as headerobj
-
-
+import os
 import time
 import unittest
-import os
+
+from src import whatthepatch as wtp
+from src.whatthepatch.patch import Change, diffobj
+from src.whatthepatch.patch import header as headerobj
 
 module_path = os.path.dirname(__file__)