In the Go language, you can use the `Transport` type in the `net/http` package to create an HTTP tunnel. HTTP tunneling is to transmit data of other protocols through the HTTP protocol, such as TCP, UDP, etc.
Here is a simple example showing how to use HTTP tunneling to transfer TCP data:
```go
package main
import (
"fmt"
"io"
"net"
"net/http"
)
func main() {
// Create an HTTP client
client := &http.Client{
Transport: &http.Transport{
Dial: func(network, addr string) (net.Conn, error) {
// Establish a TCP connection
conn, err := net.Dial(network, addr)
if err != nil {
return nil, err
}
// Send a CONNECT request to establish an HTTP tunnel
req, err := http.NewRequest("CONNECT", "www.google.com:80", nil)
if err != nil {
return nil, err
}
err = req.Write(conn)
if err != nil {
return nil, err
}
// Read the response to determine whether the establishment is successful
resp, err := http.ReadResponse(bufio.NewReader(conn), req)
if err != nil {
return nil, err
}
if resp.StatusCode != 200 {
return nil, fmt.Errorf("failed to establish HTTP tunnel")
}
// return connection
return conn, nil
},
},
}
// Send HTTP request, transmit TCP data through HTTP tunnel
resp, err := client.Get("http://www.google.com")
if err != nil {
fmt.Println(err)
return
}
defer resp.Body.Close()
io.Copy(os.Stdout, resp.Body)
}
```
In the above example, we created an HTTP client and established a TCP connection and HTTP tunnel through the `Dial` method of the `Transport` type. In the `Dial` method, we first establish a TCP connection, and then send a `CONNECT` request, requesting the establishment of an HTTP tunnel. Finally, we read the response to determine whether the establishment is successful, and if successful, return the connection.
When sending HTTP requests, we use the `client.Get` method, which automatically uses the HTTP client we created and transmits TCP data through the HTTP tunnel. Finally, we read the response body and output it to standard output.
It should be noted that the above example is just a simple demonstration, and more details need to be considered in actual use, such as error handling, connection pool management, etc.