use log package

daily.go

@@ -3,7 +3,7 @@
 package main
 
 import (
-	"fmt"
+	"log"
 	"os"
 	"sort"
 	"strconv"
@@ -38,13 +38,16 @@ func main() {
 
 	message := createMessage(yesterDay, channels, count)
 	botClient := slack.New(os.Getenv("SLACK_BOT_TOKEN"))
-	botClient.PostMessage(os.Getenv("SLACK_CHANNEL_ID"), slack.MsgOptionText(message, false))
+	_, _, err := botClient.PostMessage(os.Getenv("SLACK_CHANNEL_ID"), slack.MsgOptionText(message, false))
+	if err != nil {
+		log.Printf("can not post: %v\n", err)
+	}
 }
 
 func (client SlackClient) getConversationsForUser() []slack.Channel {
 	conversations, _, err := client.GetConversationsForUser(&slack.GetConversationsForUserParameters{})
 	if err != nil {
-		fmt.Println(err)
+		log.Printf("can not get channels: %v\n", err)
 	}
 	return conversations
 }
@@ -56,7 +59,11 @@ func createChannels(conversations []slack.Channel, now time.Time, yesterDay time
 	var count int
 	for _, conversation := range conversations {
 		params := slack.GetConversationHistoryParameters{ChannelID: conversation.ID, Limit: 1000, Latest: latest, Oldest: oldest}
-		conversationHistory, _ := userClient.GetConversationHistory(&params)
+		conversationHistory, err := userClient.GetConversationHistory(&params)
+		if err != nil {
+			log.Printf("can not get history channelID: %s, %v\n", conversation.ID, err)
+			continue
+		}
 		channel := Channel{name: conversation.Name, id: conversation.ID}
 		for _, message := range conversationHistory.Messages {
 			count++

daily_test.go

@@ -5,6 +5,7 @@ package main
 import (
 	"bytes"
 	"embed"
+	"log"
 	"net/http"
 	"os"
 	"strings"
@@ -41,7 +42,7 @@ func TestGetConversationsForUser(t *testing.T) {
 		{
 			name:   "usersConversationsError",
 			apiRes: "testdata/usersConversations/error.json",
-			want:   want{channels: []slack.Channel{}, print: "invalid_auth"},
+			want:   want{channels: []slack.Channel{}, print: "can not get channels: invalid_auth"},
 		},
 	}
 	for _, tt := range tests {
@@ -56,21 +57,21 @@ func TestGetConversationsForUser(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Helper()
 
-			orgStdout := os.Stdout
+			var buf bytes.Buffer
+			log.SetOutput(&buf)
+			defaultFlags := log.Flags()
+			log.SetFlags(0)
 			defer func() {
-				os.Stdout = orgStdout
+				log.SetOutput(os.Stderr)
+				log.SetFlags(defaultFlags)
+				buf.Reset()
 			}()
-			r, w, _ := os.Pipe()
-			os.Stdout = w
+
 			got := SlackClient{client}.getConversationsForUser()
+
 			if len(got) != len(tt.want.channels) {
 				t.Errorf("add() = %v, want %v", got, tt.want.channels)
 			}
-			w.Close()
-			var buf bytes.Buffer
-			if _, err := buf.ReadFrom(r); err != nil {
-				t.Fatalf("failed to read buf: %v", err)
-			}
 			gotPrint := strings.TrimRight(buf.String(), "\n")
 			if gotPrint != tt.want.print {
 				t.Errorf("add() = %v, want %v", gotPrint, tt.want.print)