diff --git a/.github/workflows/clang-format-check.yml b/.github/workflows/clang-format-check.yml
index 42486df..5eabf04 100644
--- a/.github/workflows/clang-format-check.yml
+++ b/.github/workflows/clang-format-check.yml
@@ -17,7 +17,7 @@ jobs:
           - "include"
           - "test"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run clang-format style check for C/C++/Protobuf programs.
         uses: jidicula/clang-format-action@v4.11.0
         with:
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 0f2735a..15f49e3 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -11,7 +11,7 @@ jobs:
     name: Build on MacOS
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: maxim-lobanov/setup-xcode@v1
         with:
           xcode-version: latest-stable
@@ -20,4 +20,4 @@ jobs:
       - name: build
         run: cmake --build build --parallel 2
       - name: test
-        run: cd build && ctest -j 2 --output-on-failure
\ No newline at end of file
+        run: cd build && ctest -j 2 --output-on-failure
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index c0a2eb3..2ff264f 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -13,7 +13,7 @@ jobs:
       matrix:
         compiler: [g++-7, g++-9, g++-11]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install compiler
         run: |
           echo "deb http://dk.archive.ubuntu.com/ubuntu/ focal main universe" | sudo tee -a /etc/apt/sources.list
@@ -32,7 +32,7 @@ jobs:
       matrix:
         compiler: [g++-8, g++-10, g++-12]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install compiler
         run: |
           echo "deb http://dk.archive.ubuntu.com/ubuntu/ focal main universe" | sudo tee -a /etc/apt/sources.list
@@ -51,7 +51,7 @@ jobs:
       matrix:
         compiler: ["15", "17"]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install compiler
         run: |
           wget https://apt.llvm.org/llvm.sh
@@ -70,7 +70,7 @@ jobs:
       matrix:
         compiler: ["16"]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install compiler
         run: |
           wget https://apt.llvm.org/llvm.sh
@@ -90,7 +90,7 @@ jobs:
         standard: [11, 14, 17, 20]
         compiler: [g++-11]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install compiler
         run: |
           sudo apt-get update
@@ -105,7 +105,7 @@ jobs:
   ci_nonstandard_features:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: cmake
         run: cmake -S . -B build -DCMAKE_CXX_COMPILER=g++ -DAMC_PEDANTIC=ON -DCMAKE_BUILD_TYPE=Debug
       - name: build
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 487c8d9..b97308c 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -15,7 +15,7 @@ jobs:
         architecture: [Win32, x64]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: cmake
         run: cmake -S . -B build -A ${{ matrix.architecture }}
         if: matrix.build_type == 'Release'
@@ -31,7 +31,7 @@ jobs:
     runs-on: windows-2019
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: cmake
         run: cmake -S . -B build -DCMAKE_CXX_FLAGS="/permissive- /std:c++latest /utf-8 /W4"
       - name: build
@@ -46,7 +46,7 @@ jobs:
         architecture: [Win32, x64]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: cmake
         run: cmake -S . -B build -A ${{ matrix.architecture }} -T ClangCL
       - name: build
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0093c63..4ca0d63 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required (VERSION 3.14)
 
 project(amc 
-  VERSION 2.5.1
+  VERSION 2.6.0.0
   DESCRIPTION "Header base library of C++ containers"
   LANGUAGES CXX
 )