.github: set latest Go versions

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 80fdc0a..57b9540 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,8 +7,8 @@
     - name: Install Go
       uses: WillAbides/setup-go-faster@main
       with:
-        go-version: 1.18.x
-    - uses: actions/checkout@v3
+        go-version: 1.21.x
+    - uses: actions/checkout@v4
       with:
          path: './src/github.com/kevinburke/ssh_config'
     # staticcheck needs this for GOPATH
@@ -23,14 +23,14 @@
   test:
     strategy:
       matrix:
-        go-version: [1.17.x, 1.18.x, 1.19.x]
+        go-version: [1.17.x, 1.18.x, 1.19.x, 1.20.x, 1.21.x]
     runs-on: ubuntu-latest
     steps:
     - name: Install Go
       uses: WillAbides/setup-go-faster@main
       with:
         go-version: ${{ matrix.go-version }}
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
          path: './src/github.com/kevinburke/ssh_config'
     - run: |