feat: implement http support

Signed-off-by: Kairee Wu <kaireewu@gmail.com>

client.go

@@ -1,6 +1,7 @@
 package krpc
 
 import (
+	"bufio"
 	"context"
 	"encoding/json"
 	"errors"
@@ -8,6 +9,8 @@ import (
 	"io"
 	"log"
 	"net"
+	"net/http"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -241,3 +244,34 @@ func dialTimeout(f newClientFunc, network, address string,
 		return result.client, result.err
 	}
 }
+
+func NewHTTPClient(conn net.Conn, opts ...Option) (*Client, error) {
+	_, _ = fmt.Fprintf(conn,
+	"CONNECT %s HTTP/1.0\n\n", defaultRPCPath)
+
+	resp, err := http.ReadResponse(bufio.NewReader(conn),
+		&http.Request{Method: http.MethodConnect})
+	if err == nil && resp.Status == connected {
+		return NewClient(conn, opts...)
+	}
+	return nil, err
+}
+
+func DialHTTP(network, address string, opts ...Option) (*Client, error) {
+	return dialTimeout(NewHTTPClient, network, address, opts...)
+}
+
+func XDial(rpcAddr string, opts ...Option) (*Client, error) {
+	parts := strings.Split(rpcAddr, "://")
+	if len(parts) != 2 {
+		return nil, fmt.Errorf("rpc: client wrong format '%s', expect protocol://addr", rpcAddr)
+	}
+	protocol, addr := parts[0], parts[1]
+
+	switch protocol {
+	case "http":
+		return DialHTTP("tcp", addr, opts...)
+	default:
+		return Dial(protocol, addr, opts...)
+	}
+}