Remove deprecated linters, specify go version in lint workflow

.github/workflows/golangci-lint.yml

@@ -16,7 +16,10 @@ jobs:
     name: lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/setup-go@v2
+      - name: Set up Go 1.15
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.15
       - uses: actions/checkout@v2
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v2
@@ -41,4 +44,4 @@ jobs:
           # skip-pkg-cache: true
 
           # Optional: if set to true then the action don't cache or restore ~/.cache/go-build.
-          # skip-build-cache: true
+          # skip-build-cache: true

.golangci.yaml

@@ -13,7 +13,6 @@ linters-settings:
 
 linters:
   enable:
-    - deadcode
     - depguard
     - errcheck
     - exportloopref
@@ -30,11 +29,9 @@ linters:
     - prealloc
     - revive
     - staticcheck
-    - structcheck
     - typecheck
     - unconvert
     - unused
-    - varcheck
   disable:
     - gochecknoglobals # we allow global variables in packages
     - gochecknoinits   # we allow inits in packages