refactor: replace cmux with connmux and add upgrade command

Author: kooksee

.gitignore

@@ -25,3 +25,4 @@ kdata
 *.log
 proto-vendor
 .gitconfig
+.local

README.md

@@ -52,6 +52,10 @@ Funk is a comprehensive Go utility library that provides enhanced error handling
 - Path and file utilities
 - String and formatting helpers
 
+### 🔀 Connection Multiplexing
+- Serve gRPC/HTTP/1/HTTP/2 on the same port (connection sniffing)
+- Package: `connmux` (see `connmux/README.md`)
+
 ## Installation
 
 ```bash

README.zh.md

@@ -52,6 +52,10 @@ Funk是一个全面的Go实用程序库，提供增强的错误处理、结果
 - 路径和文件实用程序
 - 字符串和格式化助手
 
+### 🔀 连接分流（同端口多协议）
+- 在同一个端口上同时提供 gRPC / HTTP/1 / HTTP/2（通过连接 sniff）
+- 包：`connmux`（见 `connmux/README.md`）
+
 ## 安装
 
 ```bash

closer/utils.go

@@ -5,12 +5,22 @@ import (
 	"log/slog"
 )
 
+func ErrClose(closer func() error) {
+	if closer == nil {
+		return
+	}
+
+	if err := closer(); err != nil {
+		slog.Error("failed to close error operation", "err", err)
+	}
+}
+
 func SafeClose(closer io.Closer) {
 	if closer == nil {
 		return
 	}
 
 	if err := closer.Close(); err != nil {
-		slog.Error("failed to close operation", "err", err)
+		slog.Error("failed to close io operation", "err", err)
 	}
 }