Update common Prometheus files (#2137)

Signed-off-by: prombot <prometheus-team@googlegroups.com>

.github/workflows/golangci-lint.yml

@@ -0,0 +1,29 @@
+name: golangci-lint
+on:
+  push:
+    paths:
+      - "go.sum"
+      - "go.mod"
+      - "**.go"
+      - "scripts/errcheck_excludes.txt"
+      - ".github/workflows/golangci-lint.yml"
+  pull_request:
+    paths:
+      - "go.sum"
+      - "go.mod"
+      - "**.go"
+      - "scripts/errcheck_excludes.txt"
+      - ".github/workflows/golangci-lint.yml"
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@v2
+        with:
+          version: v1.42.0

Makefile.common

@@ -83,12 +83,18 @@ PROMU_URL     := https://github.com/prometheus/promu/releases/download/v$(PROMU_
 
 GOLANGCI_LINT :=
 GOLANGCI_LINT_OPTS ?=
-GOLANGCI_LINT_VERSION ?= v1.39.0
+GOLANGCI_LINT_VERSION ?= v1.42.0
 # golangci-lint only supports linux, darwin and windows platforms on i386/amd64.
 # windows isn't included here because of the path separator being different.
 ifeq ($(GOHOSTOS),$(filter $(GOHOSTOS),linux darwin))
 	ifeq ($(GOHOSTARCH),$(filter $(GOHOSTARCH),amd64 i386))
+		# If we're in CI and there is an Actions file, that means the linter
+		# is being run in Actions, so we don't need to run it here.
+		ifeq (,$(CIRCLE_JOB))
 			GOLANGCI_LINT := $(FIRST_GOPATH)/bin/golangci-lint
+		else ifeq (,$(wildcard .github/workflows/golangci-lint.yml))
+			GOLANGCI_LINT := $(FIRST_GOPATH)/bin/golangci-lint
+		endif
 	endif
 endif