Silence net.ErrClosed errors

conn.go

@@ -194,7 +194,7 @@ func newConn(srv *Server, ic ircConn, options *connOptions) *conn {
 				break
 			}
 		}
-		if err := c.conn.Close(); err != nil {
+		if err := c.conn.Close(); err != nil && !isErrClosed(err) {
 			c.logger.Printf("failed to close connection: %v", err)
 		} else {
 			c.logger.Printf("connection closed")
@@ -232,7 +232,9 @@ func (c *conn) Close() error {
 
 func (c *conn) ReadMessage() (*irc.Message, error) {
 	msg, err := c.conn.ReadMessage()
-	if err != nil {
+	if isErrClosed(err) {
+		return nil, io.EOF
+	} else if err != nil {
 		return nil, err
 	}
 

net_go113.go

@@ -0,0 +1,11 @@
+// +build !go1.16
+
+package soju
+
+import (
+	"strings"
+)
+
+func isErrClosed(err error) bool {
+	return err != nil && strings.Contains(err.Error(), "use of closed network connection")
+}

net_go116.go

@@ -0,0 +1,12 @@
+// +build go1.16
+
+package soju
+
+import (
+	"errors"
+	"net"
+)
+
+func isErrClosed(err error) bool {
+	return errors.Is(err, net.ErrClosed)
+}