test and build against both supported Go lines

.github/workflows/ci.yml

@@ -29,24 +29,32 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        # The floor declared by go.mod and the newest stable line: the floor
+        # proves go install works for the oldest supported toolchain, the
+        # newest is what releases build with.
+        go: ["1.25", "1.26"]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v7
       - uses: actions/setup-go@v6
         with:
-          go-version-file: go.mod
+          go-version: ${{ matrix.go }}
       - run: go build ./...
       - run: go test -race ./...
 
   release-dry-run:
+    strategy:
+      fail-fast: false
+      matrix:
+        go: ["1.25", "1.26"]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7
         with:
           fetch-depth: 0
       - uses: actions/setup-go@v6
         with:
-          go-version-file: go.mod
+          go-version: ${{ matrix.go }}
       - uses: docker/setup-qemu-action@v4
       - uses: docker/setup-buildx-action@v4
       - uses: goreleaser/goreleaser-action@v7

.github/workflows/release.yml

@@ -20,7 +20,10 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-go@v6
         with:
-          go-version-file: go.mod
+          # Pinned to the newest CI-tested line rather than go.mod: the
+          # directive there is the compatibility floor, not the toolchain
+          # official binaries should be built with.
+          go-version: "1.26"
           # Release builds are hermetic: the Actions cache is writable from
           # any PR branch, so restoring it here would let a poisoned cache
           # entry reach the publishing build.