How do I rewrite / redirect from http to https in Go?

The solutions posted above are a little inflexible, especially if the external hostname is different from the local host.

Here is the code I use for HTTP->HTTPS redirects:

package main

import (
    "net"
    "log"
    "net/http"
)

var httpAddr ":8080"
var httpsAddr ":8443"

func main() {
    srv := http.Server{
        Addr: httpsAddr,
    }

    _, tlsPort, err := net.SplitHostPort(httpsAddr)
    if err != nil {
        return err
    }
    go redirectToHTTPS(tlsPort)

    srv.ListenAndServeTLS("cert.pem", "key.pem")
}

func redirectToHTTPS(tlsPort string) {
    httpSrv := http.Server{
        Addr: httpAddr,
        Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request){
            host, _, _ := net.SplitHostPort(r.Host)
            u := r.URL
            u.Host = net.JoinHostPort(host, tlsPort)
            u.Scheme="https"
            log.Println(u.String())
            http.Redirect(w,r,u.String(), http.StatusMovedPermanently)
        }),
    }
    log.Println(httpSrv.ListenAndServe())
}

If you are using standard ports (80,443) the splitting of joining of the adresses is not rquired and just setting the scheme on the URL is sufficient.

Create a handler which handles redirection to https like:

func redirectToTls(w http.ResponseWriter, r *http.Request) {
    http.Redirect(w, r, "https://IPAddr:443"+r.RequestURI, http.StatusMovedPermanently)
}

Then redirect http traffic:

go func() {
    if err := http.ListenAndServe(":80", http.HandlerFunc(redirectToTls)); err != nil {
        log.Fatalf("ListenAndServe error: %v", err)
    }
}()

package main

import (
    "fmt"
    "net/http"
)

func redirectToHttps(w http.ResponseWriter, r *http.Request) {
    // Redirect the incoming HTTP request. Note that "127.0.0.1:443" will only work if you are accessing the server from your local machine.
    http.Redirect(w, r, "https://127.0.0.1:443"+r.RequestURI, http.StatusMovedPermanently)
}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hi there!")
    fmt.Println(r.RequestURI)
}

func main() {
    http.HandleFunc("/", handler)
    // Start the HTTPS server in a goroutine
    go http.ListenAndServeTLS(":443", "cert.pem", "key.pem", nil)
    // Start the HTTP server and redirect all incoming connections to HTTPS
    http.ListenAndServe(":8080", http.HandlerFunc(redirectToHttps))
}