Simple Go reverse proxy

revproxy.go

package main

import (
        "fmt"
        "log"
        "net/http"
        "net/http/httputil"
        "strings"
)

// Reverse proxy:
//
//      localhost:8080/foo -> localhost:8081/
//      localhost:8080/bar -> localhost:8082/
func main() {
        log.Println("[main] starting application")

        fooAddr := "127.0.0.1:8081"
        go startServerFoo(fooAddr)

        barAddr := "127.0.0.1:8082"
        go startServerBar(barAddr)

        // custom proxy with a director routing based on the 1st part of the path
        proxy := &httputil.ReverseProxy{
                Director: func(req *http.Request) {
                        log.Printf("[director] req: %+v", req.URL)

                        // get first part
                        path := strings.TrimPrefix(req.URL.Path, "/")
                        parts := strings.SplitN(path, "/", 2)
                        firstPart := parts[0]

                        req.URL.Scheme = "http"
                        switch firstPart {
                        case "foo":
                                req.URL.Host = fooAddr
                        case "bar":
                                req.URL.Host = barAddr
                        }
                },
        }

        http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
                log.Printf("[proxy] handling request: %s", r.URL)
                //proxy.ServeHTTP(w, r)
        })

        // start reverse proxy server
        if err := http.ListenAndServe(":8080", nil); err != nil {
                panic(err)
        }
}

func startServerFoo(addr string) {
        mux := http.NewServeMux()
        mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
                log.Printf("[foo] received a request: %v", r)
                fmt.Fprintf(w, "foo says hi!")
        })
        log.Printf("[foo] listening on: %s", addr)
        http.ListenAndServe(addr, mux)
}

func startServerBar(addr string) {
        mux := http.NewServeMux()
        mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
                log.Printf("[bar] received a request: %v", r)
                fmt.Fprintf(w, "bar says hi!")
        })
        log.Printf("[bar] listening on: %s", addr)
        http.ListenAndServe(addr, mux)
}