[codex] Update Go version and CI matrix

.github/workflows/test.yaml

@@ -1,18 +1,39 @@
 name: Tests
-on: [push, pull_request]
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
 jobs:
   test:
+    name: Go ${{ matrix.go-version }}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        go-version:
+          - "1.21"
+          - "1.22"
+          - "1.23"
+          - "1.24"
+          - "1.25"
+          - "1.26"
+
     steps:
-      - name: Install Go
-        uses: actions/setup-go@v2
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
         with:
-          go-version: 1.16
-      - name: Checkout Code
-        uses: actions/checkout@v2
-      - name: Bootstrap environment
-        run: make bootstrap
-      - name: Lint
-        run: make lint
-      - name: Run Tests
-        run: make test
+          go-version: ${{ matrix.go-version }}
+          cache: true
+
+      - name: Build
+        run: go build ./...
+
+      - name: Test
+        run: go test -v ./...

go.mod

@@ -1,6 +1,6 @@
 module github.com/sdcoffey/big
 
-go 1.13
+go 1.21
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect