github workflows: fix the lint job

This metallb-operator v0.12 is using go v1.16, however, the lint lane
in the CI is installing the latest go.

This change fixes the version to v1.16 by first downloading go v1.16
using actions/setup-go@v2, and then calling golangci-lint with the
skip-go-installation: true.

This solution was recommended here: golangci/golangci-lint-action#75

.github/workflows/general.yml

@@ -22,11 +22,18 @@ jobs:
     - name: Check out code
       uses: actions/checkout@v2
 
+    - name: Set up Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: '1.16'
+      id: go
+
     - name: Verify
       uses: golangci/golangci-lint-action@v2
       with:
         version: v1.41.1
         args: --timeout=15m0s --verbose
+        skip-go-installation: true
 
   unit:
     runs-on: ubuntu-20.04