Add errgroup and improve error handling

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/alecthomas/kingpin/v2 v2.3.1
 	github.com/prometheus/client_golang v1.15.0
 	go.bug.st/serial v1.5.0
+	golang.org/x/sync v0.1.0
 )
 
 require (

go.sum

@@ -40,6 +40,8 @@ github.com/xhit/go-str2duration v1.2.0/go.mod h1:3cPSlfZlUHVlneIVfePFWcJZsuwf+P1
 go.bug.st/serial v1.5.0 h1:ThuUkHpOEmCVXxGEfpoExjQCS2WBVV4ZcUKVYInM9T4=
 go.bug.st/serial v1.5.0/go.mod h1:UABfsluHAiaNI+La2iESysd9Vetq7VRdpxvjx7CmmOE=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

main.go

@@ -13,6 +13,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"go.bug.st/serial"
+	"golang.org/x/sync/errgroup"
 )
 
 type Status struct {
@@ -58,10 +59,10 @@ func parser(data string) (Status, error) {
 	return result, nil
 }
 
-func recordMetrics() {
+func recordMetrics() error {
 	port, err := serial.Open(*deviceName, &serial.Mode{})
 	if err != nil {
-		log.Fatalln(err)
+		return err
 	}
 	mode := &serial.Mode{
 		BaudRate: 115200,
@@ -70,11 +71,11 @@ func recordMetrics() {
 		StopBits: serial.OneStopBit,
 	}
 	if err := port.SetMode(mode); err != nil {
-		logger.Fatalln(err)
+		return err
 	}
 	_, err = port.Write([]byte("STA\r\n"))
 	if err != nil {
-		logger.Fatalln(err)
+		return err
 	}
 
 	defer func() {
@@ -102,6 +103,8 @@ func recordMetrics() {
 		temperature.Set(stat.temp)
 		humidity.Set(stat.hum)
 	}
+
+	return err
 }
 
 var (
@@ -120,7 +123,8 @@ var (
 )
 
 func run() error {
-	go recordMetrics()
+	e := errgroup.Group{}
+	e.Go(recordMetrics)
 
 	http.Handle("/metrics", promhttp.Handler())
 	http.HandleFunc("/", func(w http.ResponseWriter, request *http.Request) {
@@ -131,12 +135,11 @@ func run() error {
 			return
 		}
 	})
-	err := http.ListenAndServe(*addr, nil)
-	if err != nil {
-		return err
-	}
+	e.Go(func() error {
+		return http.ListenAndServe(*addr, nil)
+	})
 
-	return nil
+	return e.Wait()
 }
 
 var (

main_test.go

@@ -1,6 +1,9 @@
 package main
 
-import "testing"
+import (
+	"errors"
+	"testing"
+)
 
 func TestParser(t *testing.T) {
 	tests := []struct {
@@ -49,7 +52,7 @@ func TestParser(t *testing.T) {
 
 	for _, tt := range tests {
 		stat, err := parser(tt.in)
-		if err != tt.err {
+		if !errors.Is(err, tt.err) {
 			t.Errorf("expect error got %v, want %v", stat, tt.out)
 		}
 		if stat != tt.out {