client.swift

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let builder = HelloRequest.Builder()
        builder.name = "Bob"
        
        do {
            let req = try builder.build()
            print("Client: My name is \(req.name)")
            self.post(req.data())
        } catch {
            print(error)
        }
    }
    
    func post(data: NSData) {
        let req = NSMutableURLRequest(URL: NSURL(string: "http://localhost:8080")!)
        req.HTTPMethod = "POST"
        req.HTTPBody = data
        
        let task = NSURLSession.sharedSession().dataTaskWithRequest(req) { data, response, error in
            if error != nil {
                print(error)
                return
            }
            
            do {
                let reply = try HelloReply.parseFromData(data!)
                print("Server: \(reply.response)")
            } catch {
                print(error)
            }
        }
        task.resume()
    }

}

hello.proto

syntax = "proto3";

message HelloRequest {
  string name = 2;
}

message HelloReply {
  string response = 1;
}

server.go

package main

import (
	"bytes"
	"fmt"
	"hello"
	"log"
	"net/http"

	"github.com/golang/protobuf/proto"
)

func handler(w http.ResponseWriter, r *http.Request) {

	// Unmarshal incoming request body into a HelloRequest
	// object
	req := &hello.HelloRequest{}
	buf := new(bytes.Buffer)
	buf.ReadFrom(r.Body)

	if err := proto.Unmarshal(buf.Bytes(), req); err != nil {
		log.Fatal("Unmarshaling error: ", err)
		return
	}

	// Marshal a HelloReply object to pass as the response
	reply := &hello.HelloReply{Response: "Hello, " + req.Name}
	data, err := proto.Marshal(reply)
	if err != nil {
		log.Fatal("Marshaling error: ", err)
		return
	}

	fmt.Fprintf(w, string(data[:]))
}

func main() {
	http.HandleFunc("/", handler)
	log.Fatal(http.ListenAndServe(":8080", nil))
}