golangci-lint: prevent io/ioutil from being used

The package has been deprecated since Go 1.16:

https://go.dev/doc/go1.16#ioutil

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.golangci.yml

@@ -2,6 +2,7 @@ linters:
   enable:
     - bodyclose
     - deadcode
+    - depguard
     - dogsled
     - gocyclo
     - goimports
@@ -33,6 +34,13 @@ run:
     - .*generated.*
 
 linters-settings:
+  depguard:
+    list-type: blacklist
+    include-go-root: true
+    packages:
+      # The io/ioutil package has been deprecated.
+      # https://go.dev/doc/go1.16#ioutil
+      - io/ioutil
   gocyclo:
     min-complexity: 16
   govet: