Fix panic on error in clip.TOTPCopier() when not run as a goroutine

clip/totp.go

@@ -32,6 +32,13 @@ func GenTOTP(secret string, time time.Time, forSteam bool) (string, error) {
 // Set oneTime to -1 for a one-time (non-continuous) TOTP copy.
 // For oneTime mode, this function can be used normally (not as a goroutine).
 func TOTPCopier(secret string, oneTime int, errorChan chan<- error, done <-chan bool) error {
+	var writeErrorChan func(err error)
+	if errorChan != nil {
+		writeErrorChan = func(err error) { errorChan <- err }
+	} else {
+		writeErrorChan = func(err error) {}
+	}
+
 	var forSteam bool
 	if strings.HasPrefix(secret, "steam@") {
 		secret = secret[6:]
@@ -42,16 +49,16 @@ func TOTPCopier(secret string, oneTime int, errorChan chan<- error, done <-chan
 		currentTime := time.Now()
 		token, err := GenTOTP(secret, currentTime, forSteam)
 		if err != nil {
-			errorChan <- err
+			writeErrorChan(err)
 			return err // return for when not used as goroutine; should exit on error regardless
 		}
 		err = CopyString(true, token)
 		if err != nil {
-			errorChan <- err
+			writeErrorChan(err)
 			return err // return for when not used as goroutine; should exit on error regardless
 		}
 		if oneTime != -1 {
-			errorChan <- nil
+			writeErrorChan(err)
 			time.Sleep(time.Duration(30-(currentTime.Second()%30)) * time.Second)
 		} else {
 			return nil
@@ -60,7 +67,7 @@ func TOTPCopier(secret string, oneTime int, errorChan chan<- error, done <-chan
 		// exit after sleep if indicated (will not update clipboard again)
 		select {
 		case <-done:
-			errorChan <- nil
+			writeErrorChan(nil)
 			return nil
 		default:
 		}