ci: use go-version-file instead of hardcoded Go version

The go.mod was bumped to go 1.25.0 on master, breaking CI workflows
that hardcoded GO_VERSION: '1.24'. Switch to go-version-file: 'go.mod'
so the Go version is always derived from go.mod automatically.

.github/workflows/rust-volume-server-tests.yml

@@ -25,8 +25,6 @@ concurrency:
 permissions:
   contents: read
 
-env:
-  GO_VERSION: '1.24'
 
 jobs:
   rust-unit-tests:
@@ -70,10 +68,10 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v6
 
-      - name: Set up Go ${{ env.GO_VERSION }}
+      - name: Set up Go
         uses: actions/setup-go@v6
         with:
-          go-version: ${{ env.GO_VERSION }}
+          go-version-file: 'go.mod'
 
       - name: Install protobuf compiler
         run: sudo apt-get update && sudo apt-get install -y protobuf-compiler
@@ -146,10 +144,10 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v6
 
-      - name: Set up Go ${{ env.GO_VERSION }}
+      - name: Set up Go
         uses: actions/setup-go@v6
         with:
-          go-version: ${{ env.GO_VERSION }}
+          go-version-file: 'go.mod'
 
       - name: Install protobuf compiler
         run: sudo apt-get update && sudo apt-get install -y protobuf-compiler

.github/workflows/volume-server-integration-tests.yml

@@ -28,7 +28,6 @@ permissions:
   contents: read
 
 env:
-  GO_VERSION: '1.24'
   TEST_TIMEOUT: '30m'
 
 jobs:
@@ -46,10 +45,10 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v6
 
-      - name: Set up Go ${{ env.GO_VERSION }}
+      - name: Set up Go
         uses: actions/setup-go@v6
         with:
-          go-version: ${{ env.GO_VERSION }}
+          go-version-file: 'go.mod'
 
       - name: Build SeaweedFS binary
         run: |