Yes, it is easy to build reverse proxy with Go. 1. First, use NewSingleHostReverseProxy to create a proxy pointing to the target service by importing net/http/httputil and net/url packages; 2. Set up an HTTP server in the main function and forward the request to the backend through proxy.ServeHTTP; 3. You can modify the request header through custom Director function, such as adding the X-Forwarded-By identifier; 4. Use the ModifyResponse function to process the response, such as setting the response header or recording status code; 5. You can superimpose middleware to implement logging, authentication and other functions, such as encapsulating logging Middleware for request log output; 6. Support multi-service routing, and distribute different path requests to different backend services through http.Handle and http.StripPrefix; 7. It is recommended to configure a custom http.Transport in production environment to set timeouts, enable TLS, add retry and current limit mechanisms, and use structured logs to improve observability. The whole process is simple and efficient, and you can build an extensible reverse proxy gateway in less than 50 lines of code.
Building a reverse proxy in Go is surprisingly straightforward, thanks to the net/http/httputil package, which includes a built-in ReverseProxy type. You don't need to reinvent the wheel—Go gives you the tools to create a functional and excessive reverse proxy with just a few lines of code.
Here's how to build a basic but practical reverse proxy in Go, along with some useful enhancements you might want.
1. Basic Reverse Proxy Setup
Start by importing the necessary packages:
package main
import (
"log"
"net/http"
"net/http/httputil"
""net/url"
)Now, define a function that creates a reverse proxy pointing to a target server:
func NewReverseProxy(targetHost string) *httputil.ReverseProxy {
url, _ := url.Parse(targetHost)
return httputil.NewSingleHostReverseProxy(url)
} NewSingleHostReverseProxy handles most of the heavy lifting: it rewrites headers, updates the request URL, and forwards the request to the backend.
Next, set up a simple HTTP server that uses this proxy:
func main() {
proxy := NewReverseProxy("http://localhost:3000") // assuming backend runs on port 3000
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
proxy.ServeHTTP(w, r)
})
log.Println("Reverse proxy starting on :8080")
log.Fatal(http.ListenAndServe(":8080", nil))
} Now, when you send a request to http://localhost:8080 , it will be forwarded to your backend at http://localhost:3000 .
2. Customizing Request and Response Handling
You can customize the proxy behavior by modifying the request before it's sent or inspecting the response afterward.
For example, to add a custom header to outgoing requests:
proxy := httputil.NewSingleHostReverseProxy(targetURL)
originalDirector := proxy.Director
proxy.Director = func(req *http.Request) {
originalDirector(req)
req.Header.Set("X-Forwarded-By", "my-reverse-proxy")
} The Director is a function that prepares the outbound request. We wrap the original one to preserve default behavior and add our own logic.
To modify the response (eg, log status or alter headers):
proxy.ModifyResponse = func(resp *http.Response) error {
resp.Header.Set("X-Proxy-Status", "processed")
log.Printf("Backend responded with %d", resp.StatusCode)
return nil
}This is useful for auditing, debugging, or injecting security headers.
3. Adding Middleware (Logging, Authentication, etc.)
You can layer in standard Go middleware just like in any HTTP server.
For example, a simple logging middleware:
func loggingMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
log.Printf("%s %s %s", r.RemoteAddr, r.Method, r.URL)
next.ServeHTTP(w, r)
})
}Wrap your proxy handler:
http.HandleFunc("/", loggingMiddleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
proxy.ServeHTTP(w, r)
})).ServeHTTP) Or, more cleanly, use http.StripPrefix and http.Handle if you're routing multiple paths.
4. Multiple Services (Routing by Path)
You can route different paths to different backends:
func main() {
service1 := NewReverseProxy("http://localhost:3001")
service2 := NewReverseProxy("http://localhost:3002")
http.Handle("/api/users/", http.StripPrefix("/api/users", service1))
http.Handle("/api/products/", http.StripPrefix("/api/products", service2))
log.Println("API gateway running on :8080")
log.Fatal(http.ListenAndServe(":8080", nil))
} StripPrefix removes the matched prefix before forwarding, so /api/users/list becomes /list at the backend.
Final Notes
- The
ReverseProxyhandles most header rewrites (likeHost,X-Forwarded-For) automatically. - For production use, consider:
- Adding timeouts via a custom
http.Transport - Enabling TLS (HTTPS)
- Adding retries, circuit breakers, or rate limiting
- Using structured logging
- Adding timeouts via a custom
Here's a minimum timeout tweak:
transport := &http.Transport{
TLSHandshakeTimeout: 10 * time.Second,
ResponseHeaderTimeout: 10 * time.Second,
MaxIdleConnsPerHost: 10,
}
proxy.Transport = transportBuilding a reverse proxy in Go isn't just educational—it's practical. With under 50 lines of code, you can have a working gateway that you can extend for load balancing, auth, observability, or API aggregation.
Basically, httputil.ReverseProxy does the hard work; you just need to glue it together.
The above is the detailed content of Building a Reverse Proxy in Go. For more information, please follow other related articles on the PHP Chinese website!
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