Feat: rewritre http client with native string

Author: PuerNya

protocol/http/client.go

@@ -4,10 +4,11 @@ import (
 	std_bufio "bufio"
 	"context"
 	"encoding/base64"
+	"fmt"
 	"net"
 	"net/http"
-	"net/url"
 	"os"
+	"strings"
 
 	"github.com/sagernet/sing/common/buf"
 	"github.com/sagernet/sing/common/bufio"
@@ -65,42 +66,52 @@ func (c *Client) DialContext(ctx context.Context, network string, destination M.
 	if err != nil {
 		return nil, err
 	}
-	request := &http.Request{
-		Method: http.MethodConnect,
-		URL: &url.URL{
-			Host: destination.String(),
-		},
-		Header: http.Header{
-			"Proxy-Connection": []string{"Keep-Alive"},
-		},
-	}
-	if c.path != "" {
-		err = URLSetPath(request.URL, c.path)
-		if err != nil {
-			return nil, err
-		}
+	URL := destination.String()
+	HeaderString := "CONNECT " + URL + " HTTP/1.1\r\n"
+	tempHeaders := map[string][]string{
+		"Host":             {destination.String()},
+		"User-Agent":       {"Go-http-client/1.1"},
+		"Proxy-Connection": {"Keep-Alive"},
 	}
+
 	for key, valueList := range c.headers {
-		request.Header.Set(key, valueList[0])
-		for _, value := range valueList[1:] {
-			request.Header.Add(key, value)
-		}
+		tempHeaders[key] = valueList
 	}
+
+	if c.path != "" {
+		tempHeaders["Path"] = []string{c.path}
+	}
+
 	if c.username != "" {
 		auth := c.username + ":" + c.password
-		request.Header.Add("Proxy-Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(auth)))
+		if _, ok := tempHeaders["Proxy-Authorization"]; ok {
+			tempHeaders["Proxy-Authorization"][len(tempHeaders["Proxy-Authorization"])] = "Basic " + base64.StdEncoding.EncodeToString([]byte(auth))
+		} else {
+			tempHeaders["Proxy-Authorization"] = []string{"Basic " + base64.StdEncoding.EncodeToString([]byte(auth))}
+		}
+	}
+	for key, valueList := range tempHeaders {
+		HeaderString += key + ": " + strings.Join(valueList, "; ") + "\r\n"
 	}
-	err = request.Write(conn)
+
+	HeaderString += "\r\n"
+
+	_, err = fmt.Fprintf(conn, "%s", HeaderString)
+
 	if err != nil {
 		conn.Close()
 		return nil, err
 	}
+
 	reader := std_bufio.NewReader(conn)
-	response, err := http.ReadResponse(reader, request)
+
+	response, err := http.ReadResponse(reader, nil)
+
 	if err != nil {
 		conn.Close()
 		return nil, err
 	}
+
 	if response.StatusCode == http.StatusOK {
 		if reader.Buffered() > 0 {
 			buffer := buf.NewSize(reader.Buffered())