Golang socks5 proxy client - go

Question

I'm trying to make a proxy:
I need to listen to port 1080 (socks 5), and complete a request to a destination using an external ip:port socks 5, I managed to open this connection with the external ip, but I don't know how I could complete the request to the target destination using that external ip.
could someone help me with this?
package main
import (
"bufio"
"errors"
"fmt"
"io"
"log"
"net"
)
const (
ConnectCommand = uint8(1)
BindCommand = uint8(2)
AssociateCommand = uint8(3)
ipv4Address = uint8(1)
fqdnAddress = uint8(3)
ipv6Address = uint8(4)
)
type AddrSpec struct {
FQDN string
IP net.IP
Port int
}
func main() {
l, err := net.Listen("tcp", "127.0.0.1:1080")
if err != nil {
fmt.Print(err)
}
defer l.Close()
for {
conn, err := l.Accept()
if err != nil {
fmt.Print(err)
}
go handle(conn)
}
}
func handle(conn net.Conn) {
defer func() {
_ = conn.Close()
}()
bufConn := bufio.NewReader(conn)
version := []byte{0}
if _, err := bufConn.Read(version); err != nil {
log.Fatalf("cannot read version: %s", err.Error())
}
if version[0] != uint8(5) {
log.Fatalf("unsupported SOCKS version: %v", version)
}
socks5ExternalConn, err := net.Dial("tcp", externalSOCKS5Proxy())
if err != nil {
log.Printf("Connection error: %s", err.Error())
}
dest, err := readAddrSpec(bufConn)
if err != nil {
}
// how i can send request to server with external conn?
}
func externalSOCKS5Proxy() string {
return "externalip:externalport"
}
func readAddrSpec(r io.Reader) (*AddrSpec, error) {
d := &AddrSpec{}
// Get the address type
addrType := []byte{0}
if _, err := r.Read(addrType); err != nil {
return nil, err
}
// Handle on a per type basis
switch addrType[0] {
case ipv4Address:
addr := make([]byte, 4)
if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
return nil, err
}
d.IP = net.IP(addr)
case ipv6Address:
addr := make([]byte, 16)
if _, err := io.ReadAtLeast(r, addr, len(addr)); err != nil {
return nil, err
}
d.IP = net.IP(addr)
case fqdnAddress:
if _, err := r.Read(addrType); err != nil {
return nil, err
}
addrLen := int(addrType[0])
fqdn := make([]byte, addrLen)
if _, err := io.ReadAtLeast(r, fqdn, addrLen); err != nil {
return nil, err
}
d.FQDN = string(fqdn)
default:
return nil, errors.New("unrecognizedAddrType")
}
// Read the port
port := []byte{0, 0}
if _, err := io.ReadAtLeast(r, port, 2); err != nil {
return nil, err
}
d.Port = (int(port[0]) << 8) | int(port[1])
return d, nil
}