enable some more linters

.golangci.yml

@@ -0,0 +1,23 @@
+linters:
+  enable-all: false
+  enable:
+    - structcheck
+    - varcheck
+    - ineffassign
+    - typecheck
+    - megacheck
+    - deadcode
+    - govet
+    - errcheck
+    - goimports
+    - depguard
+    - goconst
+    - unconvert
+    - gocritic
+
+linters-settings:
+  depguard:
+    list-type: whitelist
+    packages:
+      - github.com/mmcloughlin/avo
+      - golang.org/x/arch/x86