build: use go toolchain

.forgejo/workflows/test.yml

@@ -44,6 +44,16 @@ jobs:
         with:
           go-version-file: go.mod
 
+      - name: validate go version
+        run: |
+          set -ex
+          toolchain=$(grep -oP '(?<=toolchain ).+' go.mod)
+          version=$(go version | cut -d' ' -f3)
+          if [ "$toolchain" != "$version" ]; then
+            echo "go version mismatch: $toolchain <> $version"
+            exit 1
+          fi
+
       - run: make vet
 
       - run: make build

go.mod

@@ -1,6 +1,8 @@
 module gitea.com/gitea/act_runner
 
-go 1.23.3
+go 1.23
+
+toolchain go1.23.3
 
 require (
 	code.gitea.io/actions-proto-go v0.4.0