Add linting support

- add lint target in Makefile
- add golangci-lint configuration

.golangci.yml

@@ -0,0 +1,64 @@
+---
+output:
+  sort-results: true
+
+linters-settings:
+  goheader:
+    values:
+      const:
+        ORGANIZATION: CAcert Inc.
+    template: |-
+      Copyright {{ YEAR-RANGE }} {{ ORGANIZATION }}
+      SPDX-License-Identifier: Apache-2.0
+
+      Licensed under the Apache License, Version 2.0 (the "License");
+      you may not use this file except in compliance with the License.
+      You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+      See the License for the specific language governing permissions and
+      limitations under the License.
+  goimports:
+    local-prefixes: git.cacert.org/oidc_idp
+  misspell:
+    locale: "US"
+    ignore-words:
+      - CAcert
+
+linters:
+  disable-all: false
+  enable:
+    - bodyclose
+    - containedctx
+    - contextcheck
+    - cyclop
+    - decorder
+    - errorlint
+    - exportloopref
+    - forbidigo
+    - forcetypeassert
+    - gocognit
+    - goconst
+    - gocritic
+    - gofmt
+    - goheader
+    - goimports
+    - gomnd
+    - gosec
+    - lll
+    - makezero
+    - misspell
+    - nakedret
+    - nestif
+    - nlreturn
+    - nolintlint
+    - predeclared
+    - revive
+    - rowserrcheck
+    - sqlclosecheck
+    - wrapcheck
+    - wsl

Makefile

@@ -25,11 +25,14 @@ translations: $(TRANSLATIONS) $(GOFILES)
 		goi18n merge active.*.toml translate.*.toml; \
 	fi
 
+lint: $(GOFILES)
+	golangci-lint run --verbose
+
 cacert-idp: go.sum $(GOFILES) $(TEMPLATES) translations $(RESOURCES)
 	CGO_ENABLED=0 go build -o $@ ./cmd/idp.go
 
 clean:
 	rm -rf cacert-idp ui/css ui/js ui/images
 
-.PHONY: all translations clean
+.PHONY: all translations clean lint