Add golangci-lint to CI and resolve warnings

Signed-off-by: Austin Vazquez <macedonv@amazon.com>

.github/workflows/main.yml

@@ -22,6 +22,25 @@ jobs:
       with:
         working-directory: src/github.com/containerd/fuse-overlayfs-snapshotter
 
+  linters:
+    name: Linters
+    permissions:
+      contents: read # for actions/checkout to fetch code
+      pull-requests: read # for golangci/golangci-lint-action to fetch pull requests
+    runs-on: ubuntu-22.04
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          path: src/github.com/containerd/fuse-overlayfs-snapshotter
+      - uses: actions/setup-go@v5
+        with:
+          go-version: 1.21.x
+      - uses: golangci/golangci-lint-action@v6
+        with:
+          version: v1.63.4
+          working-directory: src/github.com/containerd/fuse-overlayfs-snapshotter
+
   test:
     runs-on: ubuntu-22.04
     timeout-minutes: 30

.golangci.yml

@@ -0,0 +1,25 @@
+linters:
+  enable:
+    - copyloopvar
+    - depguard
+    - gofmt
+    - gosec
+    - govet
+    - ineffassign
+    - misspell
+    - nolintlint
+    - staticcheck
+    - tenv
+    - unconvert
+    - unused
+  disable:
+    - errcheck
+    - revive
+
+linters-settings:
+  depguard:
+    rules:
+      main:
+        deny:
+          - pkg: "io/ioutil"
+            desc: use "io" or "os" instead