Enable gochecknoinits linter and fix violations

* enables `gochecknoinits` linter in `.golintci.yaml
* refactors receiver plugins to require explicit `Register` call instead
  of implicit `init`
* updates `app.go` to explicitly register all receiver plugins guarded
  by `sync.Once`
* updates recevier tests to explicitly call `Register` during `TestMain`
* adds a `nolint:gochecknoinits` in `trie_test` to allow developer debug
  logging

Author: drawks

.golangci.yml

@@ -11,9 +11,9 @@ linters:
     - govet
     - unparam
     - bodyclose
+    - gochecknoinits
 
     # enabled in carbonapi
-    # - gochecknoinits
     # - gosec
 
     # The linters we need to enable ASAP.

carbon/app.go

@@ -24,12 +24,12 @@ import (
 	"github.com/go-graphite/go-carbon/tags"
 	"github.com/lomik/zapwriter"
 
-	// register receivers
-	_ "github.com/go-graphite/go-carbon/receiver/http"
-	_ "github.com/go-graphite/go-carbon/receiver/kafka"
-	_ "github.com/go-graphite/go-carbon/receiver/pubsub"
-	_ "github.com/go-graphite/go-carbon/receiver/tcp"
-	_ "github.com/go-graphite/go-carbon/receiver/udp"
+	// receivers
+	http_receiver "github.com/go-graphite/go-carbon/receiver/http"
+	kafka_receiver "github.com/go-graphite/go-carbon/receiver/kafka"
+	pubsub_receiver "github.com/go-graphite/go-carbon/receiver/pubsub"
+	tcp_receiver "github.com/go-graphite/go-carbon/receiver/tcp"
+	udp_receiver "github.com/go-graphite/go-carbon/receiver/udp"
 )
 
 type NamedReceiver struct {
@@ -68,6 +68,8 @@ type App struct {
 	FlushTraces    func()
 }
 
+var registerPluginsOnce sync.Once
+
 // New App instance
 func New(configFilename string) *App {
 	app := &App{
@@ -77,6 +79,15 @@ func New(configFilename string) *App {
 		exit:           make(chan bool),
 	}
 
+	// Register all receivers explicitly
+	registerPluginsOnce.Do(func() {
+		http_receiver.Register()
+		kafka_receiver.Register()
+		pubsub_receiver.Register()
+		tcp_receiver.Register()
+		udp_receiver.Register()
+	})
+
 	return app
 }
 

carbonserver/trie_test.go

@@ -21,6 +21,7 @@ import (
 	"go.uber.org/zap"
 )
 
+// nolint:gochecknoinits
 func init() { log.SetFlags(log.Lshortfile) }
 
 type logf interface {

receiver/http/http.go

@@ -18,7 +18,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-func init() {
+func Register() {
 	receiver.Register(
 		"http",
 		func() interface{} { return NewOptions() },

receiver/http/http_test.go

@@ -12,6 +12,10 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestMain(m *testing.M) {
+	Register()
+}
+
 func TestHttp(t *testing.T) {
 	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
 	if err != nil {

receiver/kafka/kafka.go

@@ -23,7 +23,7 @@ import (
 	"go.uber.org/zap"
 )
 
-func init() {
+func Register() {
 	receiver.Register(
 		"kafka",
 		func() interface{} { return NewOptions() },

receiver/pubsub/pubsub.go

@@ -26,7 +26,7 @@ import (
 // the allocation overhead of repeatedly calling gzip.NewReader
 var gzipPool sync.Pool
 
-func init() {
+func Register() {
 	receiver.Register(
 		"pubsub",
 		func() interface{} { return NewOptions() },

receiver/pubsub/pubsub_test.go

@@ -21,6 +21,10 @@ var (
 	testSub     = "test-sub"
 )
 
+func TestMain(m *testing.M) {
+	Register()
+}
+
 func newTestClient() (*pstest.Server, *pubsub.Topic, *pubsub.Client, error) {
 	ctx := context.Background()
 	srv := pstest.NewServer()

receiver/tcp/tcp.go

@@ -24,7 +24,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-func init() {
+func Register() {
 	receiver.Register(
 		"tcp",
 		func() interface{} { return NewOptions() },

receiver/tcp/tcp_test.go

@@ -16,6 +16,10 @@ type tcpTestCase struct {
 	rcvChan  chan *points.Points
 }
 
+func TestMain(m *testing.M) {
+	Register()
+}
+
 func newTCPTestCase(t *testing.T, protocol string) *tcpTestCase {
 	test := &tcpTestCase{
 		T: t,