Add CI workflow to lint and check formatting of Go code

On every push and pull request that affects relevant files, and periodically, lint and check formatting of the
repository's Go module.

Author: per1234

.github/workflows/check-go.yml

@@ -0,0 +1,71 @@
+name: Check Go
+
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    paths:
+      - ".github/workflows/check-go.yml"
+      - "Taskfile.yml"
+      - "**.go"
+  pull_request:
+    paths:
+      - ".github/workflows/check-go.yml"
+      - "Taskfile.yml"
+      - "**.go"
+  schedule:
+    # Run every Tuesday at 8 AM UTC to catch breakage caused by changes to tools.
+    - cron: "0 8 * * TUE"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  check-errors:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/actions/setup-taskfile@master
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Check for errors
+        run: task go:vet
+
+  check-style:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/actions/setup-taskfile@master
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Check style
+        run: task --silent go:lint
+
+  check-formatting:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/actions/setup-taskfile@master
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Format code
+        run: task go:format
+
+      - name: Check formatting
+        run: git diff --color --exit-code

README.md

@@ -1,3 +1,5 @@
+[![Check Go status](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-go.yml/badge.svg)](https://github.com/arduino/libraries-repository-engine/actions/workflows/check-go.yml)
+
 BUILD
 ----------------------------
 

Taskfile.yml

@@ -15,3 +15,34 @@ tasks:
     desc: Run unit tests
     cmds:
       - go test -v -short -run '{{default ".*" .GO_TEST_REGEX}}' {{default "-timeout 10m -coverpkg=./... -covermode=atomic" .GO_TEST_FLAGS}} -coverprofile=coverage_unit.txt {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}
+
+  go:check:
+    desc: Check for problems with Go code
+    deps:
+      - task: go:vet
+      - task: go:lint
+
+  go:vet:
+    desc: Check for errors in Go code
+    cmds:
+      - go vet {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}
+
+  go:lint:
+    desc: Lint Go code
+    cmds:
+      - |
+        PROJECT_PATH="$PWD"
+        # `go get` and `go list` commands must be run from a temporary folder to avoid polluting go.mod
+        cd "$(mktemp -d "${TMPDIR-${TMP-/tmp}}/task-temporary-XXXXX")"
+        go get golang.org/x/lint/golint
+        GOLINT_PATH="$(go list -f '{{"{{"}}.Target{{"}}"}}' golang.org/x/lint/golint || echo "false")"
+        # `golint` must be run from the module folder
+        cd "$PROJECT_PATH"
+        "$GOLINT_PATH" \
+          {{default "-min_confidence 0.8 -set_exit_status" .GO_LINT_FLAGS}} \
+          {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}
+
+  go:format:
+    desc: Format Go code
+    cmds:
+      - go fmt {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}