Update Actions workflow to follow Go version in go.mod

Author: tsuzu

.github/workflows/go.yml

@@ -13,15 +13,15 @@ jobs:
       GO111MODULE: on
 
     steps:
-    - name: Set up Go 1.15
-      uses: actions/setup-go@v1
+    - name: Set up Go
+      uses: actions/setup-go@v5
       with:
-        go-version: 1.15
+        go-version-file: 'go.mod'
       id: go
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
-    - uses: actions/cache@v1
+    - uses: actions/cache@v4
       with:
         path: ~/go/pkg/mod
         key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}