fix: 修复核心bug并完善API

- 修复NewRequest系列函数不返回opt错误的问题
- 修复prepare()幂等性问题，支持请求重试
- 修复defaultDialTLSFunc的ServerName解析错误
- 修复Client.Clone()并发安全问题
- 补齐Client.Trace/Connect方法
- 新增Request.HTTPClient/Client方法
- 增强NewSimpleRequest错误处理的健壮性

client.go

@@ -325,3 +325,21 @@ func (c *Client) NewSimpleRequestWithContext(ctx context.Context, url, method st
 	}
 	return req
 }
+
+// Trace 发送 TRACE 请求
+func (c *Client) Trace(url string, opts ...RequestOpt) (*Response, error) {
+	req, err := c.NewRequest(url, http.MethodTrace, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return req.Do()
+}
+
+// Connect 发送 CONNECT 请求
+func (c *Client) Connect(url string, opts ...RequestOpt) (*Response, error) {
+	req, err := c.NewRequest(url, http.MethodConnect, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return req.Do()
+}

dialer.go

@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 	"fmt"
 	"net"
+	"strings"
 	"time"
 )
 
@@ -119,8 +120,11 @@ func defaultDialTLSFunc(ctx context.Context, network, addr string) (net.Conn, er
 	if tlsConfig.ServerName == "" && !tlsConfig.InsecureSkipVerify {
 		host, _, err := net.SplitHostPort(addr)
 		if err != nil {
-			// addr 可能没有端口，直接用 addr
-			host = addr
+			if idx := strings.LastIndex(addr, ":"); idx > 0 {
+				host = addr[:idx]
+			} else {
+				host = addr
+			}
 		}
 		tlsConfig = tlsConfig.Clone() // 避免修改原 config
 		tlsConfig.ServerName = host

request.go

@@ -84,12 +84,27 @@ func newRequest(ctx context.Context, urlStr string, method string, opts ...Reque
 
 // NewRequest 创建新请求
 func NewRequest(url, method string, opts ...RequestOpt) (*Request, error) {
-	return newRequest(context.Background(), url, method, opts...)
+	req, err := newRequest(context.Background(), url, method, opts...)
+	if err != nil {
+		return nil, err
+	}
+	if req.err != nil {
+		return nil, req.err
+	}
+	return req, nil
 }
 
 // NewRequestWithContext 创建新请求（带 context）
 func NewRequestWithContext(ctx context.Context, url, method string, opts ...RequestOpt) (*Request, error) {
-	return newRequest(ctx, url, method, opts...)
+	req, err := newRequest(ctx, url, method, opts...)
+	if err != nil {
+		return nil, err
+	}
+	// 新增
+	if req.err != nil {
+		return nil, req.err
+	}
+	return req, nil
 }
 
 // NewSimpleRequest 创建新请求（忽略错误，支持链式调用）
@@ -190,7 +205,6 @@ func (r *Request) SetMethod(method string) *Request {
 	if r.err != nil {
 		return r
 	}
-
 	method = strings.ToUpper(method)
 	if !validMethod(method) {
 		r.err = wrapError(ErrInvalidMethod, "method: %s", method)
@@ -249,6 +263,10 @@ func (r *Request) SetRawRequest(httpReq *http.Request) *Request {
 	}
 	r.httpReq = httpReq
 	r.doRaw = true
+	if httpReq == nil {
+		r.err = fmt.Errorf("httpReq cannot be nil")
+		return r
+	}
 	return r
 }
 
@@ -270,6 +288,29 @@ func (r *Request) SetAutoFetch(auto bool) *Request {
 	return r
 }
 
+// HTTPClient 获取底层 http.Client（只读）
+func (r *Request) HTTPClient() (*http.Client, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+
+	if r.httpClient != nil {
+		return r.httpClient, nil
+	}
+
+	// 如果还没构建，先准备
+	if err := r.prepare(); err != nil {
+		return nil, err
+	}
+
+	return r.httpClient, nil
+}
+
+// Client 获取关联的 Client（只读）
+func (r *Request) Client() *Client {
+	return r.client
+}
+
 // Do 执行请求
 func (r *Request) Do() (*Response, error) {
 	// 检查累积的错误

request_body.go

@@ -336,17 +336,18 @@ func (r *Request) prepare() error {
 	if r.applied {
 		return nil
 	}
-	defer func() { r.applied = true }()
+
 	// 即使 raw 模式也要确保有 httpClient
 	if r.httpClient == nil {
 		var err error
 		r.httpClient, err = r.buildHTTPClient()
 		if err != nil {
-			return err
+			return err // ← 失败时不设置 applied
 		}
 	}
 	// 原始模式不修改请求内容
 	if r.doRaw {
+		r.applied = true
 		return nil
 	}
 
@@ -408,7 +409,8 @@ func (r *Request) prepare() error {
 	// 注入配置到 context
 	r.execCtx = injectRequestConfig(r.ctx, r.config)
 	r.httpReq = r.httpReq.WithContext(r.execCtx)
-
+	
+	r.applied = true
 	return nil
 }
 

response.go

@@ -36,6 +36,9 @@ func (r *Response) Body() *Body {
 
 // Close 关闭响应体
 func (r *Response) Close() error {
+	if r == nil {
+		return nil
+	}
 	if r.body != nil && r.body.raw != nil {
 		return r.body.raw.Close()
 	}
@@ -44,6 +47,9 @@ func (r *Response) Close() error {
 
 // CloseWithClient 关闭响应体并关闭空闲连接
 func (r *Response) CloseWithClient() error {
+	if r == nil {
+		return nil
+	}
 	if r.httpClient != nil {
 		r.httpClient.CloseIdleConnections()
 	}