diff --git a/msgr.go b/msgr.go
index f849680..105be08 100644
--- a/msgr.go
+++ b/msgr.go
@@ -35,10 +35,12 @@ func msgrPostHandler(w http.ResponseWriter, req *http.Request, chs []MessageChan
 	channel := req.FormValue("channel")
 	msg := req.FormValue("msg")
 	if channel == "" || msg == "" || req.Method != "POST" {
+		log.Printf("[warn] invalid request: method=%s channel=%s, msg=%s", req.Method, channel, msg)
 		code := http.StatusBadRequest
 		http.Error(w, http.StatusText(code), code)
 		return
 	}
+	log.Printf("[debug] post to channel=%s, msg=%s", channel, msg)
 	for _, ch := range chs {
 		ch.PostMsgr(req)
 	}
diff --git a/nopaste.go b/nopaste.go
index d7bad5f..ae6b33f 100644
--- a/nopaste.go
+++ b/nopaste.go
@@ -20,6 +20,8 @@ const Root = "/np"
 
 var config *Config
 
+var Debug = false
+
 type nopasteContent struct {
 	Text      string
 	Channel   string
@@ -125,6 +127,7 @@ func serveHandler(w http.ResponseWriter, req *http.Request, chs []MessageChan) {
 
 func saveContent(np nopasteContent, chs []MessageChan) (string, int) {
 	if np.Text == "" {
+		log.Println("[warn] empty text")
 		return Root, http.StatusFound
 	}
 	data := []byte(np.Text)
diff --git a/slack.go b/slack.go
index 3785d22..e28a8f6 100644
--- a/slack.go
+++ b/slack.go
@@ -3,7 +3,7 @@ package nopaste
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"math"
 	"net/http"
@@ -47,6 +47,7 @@ func (ch SlackMessageChan) PostNopaste(np nopasteContent, url string) {
 		IconURL:   np.IconURL,
 		LinkNames: np.LinkNames,
 	}
+	log.Printf("[debug] post to slack: %#v", msg)
 	select {
 	case ch <- msg:
 	default:
@@ -70,6 +71,7 @@ func (ch SlackMessageChan) PostMsgr(req *http.Request) {
 	if _notice := req.FormValue("notice"); _notice == "0" {
 		msg.LinkNames = 1
 	}
+	log.Printf("[debug] post to slack: %#v", msg)
 	select {
 	case ch <- msg:
 	default:
@@ -95,7 +97,7 @@ func (a *SlackAgent) Post(m SlackMessage) error {
 	if resp.StatusCode == http.StatusOK {
 		return nil
 	}
-	if body, err := ioutil.ReadAll(resp.Body); err == nil {
+	if body, err := io.ReadAll(resp.Body); err == nil {
 		return fmt.Errorf("failed post to slack:%s", body)
 	} else {
 		return err