Upgrade golangci-lint to v1.20.0 (#351)

Author: corneliusweig

hack/run-lint.sh

@@ -23,7 +23,7 @@ gopath="$(go env GOPATH)"
 if ! [[ -x "$gopath/bin/golangci-lint" ]]; then
   echo >&2 'Installing golangci-lint'
   curl --silent --fail --location \
-    https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b "$gopath/bin" v1.19.1
+    https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b "$gopath/bin" v1.20.0
 fi
 
 # configured by .golangci.yml