Golang HTTP Client using SOCKS5 proxy and DialContext

socks5_proxy.go

// Golang example that creates an http client that leverages a SOCKS5 proxy and a DialContext
func NewClientFromEnv() (*http.Client, error) {
	proxyHost := os.Getenv("PROXY_HOST")

	baseDialer := &net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
	}
	var dialContext DialContext

	if proxyHost != "" {
		dialSocksProxy, err := proxy.SOCKS5("tcp", proxyHost, nil, baseDialer)
		if err != nil {
			return nil, errors.Wrap(err, "Error creating SOCKS5 proxy")
		}
		if contextDialer, ok := dialSocksProxy.(proxy.ContextDialer); ok {
			dialContext = contextDialer.DialContext
		} else {
			return nil, errors.New("Failed type assertion to DialContext")
		}
		logger.Debug("Using SOCKS5 proxy for http client",
			zap.String("host", proxyHost),
		)
	} else {
		dialContext = (baseDialer).DialContext
	}

	httpClient = newClient(dialContext)
	return httpClient, nil
}

func newClient(dialContext DialContext) *http.Client {
	return &http.Client{
		Transport: &http.Transport{
			Proxy:                 http.ProxyFromEnvironment,
			DialContext:           dialContext,
			MaxIdleConns:          10,
			IdleConnTimeout:       60 * time.Second,
			TLSHandshakeTimeout:   10 * time.Second,
			ExpectContinueTimeout: 1 * time.Second,
			MaxIdleConnsPerHost:   runtime.GOMAXPROCS(0) + 1,
		},
	}
}

Hm. Why do I need all this DialContext: dialContext when it already uses http.ProxyFromEnvironment?

this code could use any proxy at all, not just one from the environment, which is quite limiting, if say, for instance, you wanted to use 10 different proxies at the same time, or round robin between them, etc...

I agree in this example, to make it clearer, I'd not use os.Getenv("PROXY_HOST") and not http.ProxyFromEnvironment!

Ah makes sense, thanks

in this example, to make it clearer, I'd not use os.Getenv("PROXY_HOST") and not http.ProxyFromEnvironment!

How to use it then? I can't see how I can pass my SOCKS5 proxy setting to the code.

Would you give another complete demo code to use it please?

resp, err := http.Get("http://example.com/") 
if err != nil { // handle error } 

defer resp.Body.Close() 
body, err := ioutil.ReadAll(resp.Body)

in this example, to make it clearer, I'd not use os.Getenv("PROXY_HOST") and not http.ProxyFromEnvironment!

How to use it then? I can't see how I can pass my SOCKS5 proxy setting to the code.

Would you give another complete demo code to use it please?

resp, err := http.Get("http://example.com/") 
if err != nil { // handle error } 

defer resp.Body.Close() 
body, err := ioutil.ReadAll(resp.Body)

client := NewClientFromEnv()
resp, err := client.Get("http://example.com")

client := NewClientFromEnv()
resp, err := client.Get("http://example.com")

Thanks, and where can I find the definition of such NewClientFromEnv() please?

Thanks, and where can I find the definition of such NewClientFromEnv() please?

@suntong, Here it is. It is a part of snippet

Another way to get the dial context:

    dialer, err := proxy.SOCKS5("tcp", proxyUrl, nil, proxy.Direct)
    dialContext := func(ctx context.Context, network, address string) (net.Conn, error) {
        return dialer.Dial(network, address)
    }

Source: https://stackoverflow.com/a/63661992