server: Expose `http` and `grpc` listen addresses.

[kavirajk]

The main rationale is for "choosing" random unbinded port for testing.

It's one of the Go's idiom to pass port number 0 to enforce Go's net's package to bind to some random port that is free.

example:

package main

import (
    "log"
    "net"
    "net/http"
    "time"

    "google.golang.org/grpc"
)

func main() {
    httpListener, err := net.Listen("tcp", "0.0.0.0:0")
    if err != nil {
        panic(err)
    }

    grpcListener, err := net.Listen("tcp", "0.0.0.0:0")
    if err != nil {
        panic(err)
    }

    h := http.Server{}
    go func() {
        log.Println("http serving at", httpListener.Addr())
        h.Serve(httpListener)
    }()

    g := grpc.Server{}
    go func() {
        log.Println("grpc serving at", grpcListener.Addr())
        g.Serve(grpcListener)
    }()

    time.Sleep(20 * time.Second)
}

And that will bind random "unassigned" port.

2022/08/08 16:51:49 grpc serving at [::]:35359
2022/08/08 16:51:49 http serving at [::]:44671

The problem is, currently there is no way to know what those ports are when using server.Server.

This PR exposes those addresses so that, we can start the test server easily and pass on the listen addresses to all it's clients.

Signed-off-by: Kaviraj kavirajkanagaraj@gmail.com

[bboreham]

Ah, never mind, the Server object isn't constructed till much later.

[kavirajk]

Thanks @bboreham for the review :)

can you also merge it? (I can happily vendor it on Loki then :))