Very quick example of an HTTP client that connects to a server and posts URLencoded key-value pairs

salclient.go

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"strings"
)

// CheckinClient is just an example of what you might collect into a "client" struct.
type CheckinClient struct {
	URL      string
	User     string
	Password string
}

func (c *CheckinClient) Checkin(values url.Values) error {
	// Create a new POST request with the urlencoded checkin values
	req, err := http.NewRequest("POST", c.URL, strings.NewReader(values.Encode()))
	if err != nil {
		return fmt.Errorf("failed to create request: %s", err)
	}

	// The endpoint requires basic authentication, so set the username/password
	req.SetBasicAuth(c.User, c.Password)
	
	// We're sending URLEncoded data in the body, so tell the server what to expect
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	
	// Execute the request
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return fmt.Errorf("failed to checkin: %s", err)
	}
	defer resp.Body.Close()
	
	// Copy the body to the console in case there is any response
	io.Copy(os.Stdout, resp.Body)
	return nil
}

func main() {
	// Make a fake checkin server that we can pretend to connect to
	fakeCheckinServer := httptest.NewServer(http.HandlerFunc(logRequest))

	// Create a "client" with the stuff that's the same for every request
	config := &CheckinClient{
		URL:      fakeCheckinServer.URL + "/checkin/",
		User:     "sal",
		Password: "superSECRET",
	}
	
	// Execute a checkin, providing the data to send to the checkin endpoint
	config.Checkin(url.Values{
		"serial":      {"abcde"},
		"key":         {"private_key_or_auth_token_or_whatever"},
		"name":        {"gopher"},
		"disk_size":   {"42"},
		"sal_version": {"1"},
	})
}

// logRequest is just a dummy "in process" thing that pretends to be the remote server and prints out what it gets
func logRequest(w http.ResponseWriter, r *http.Request) {
	log.Printf("Path: %q", r.URL.Path)
	if err := r.ParseForm(); err != nil {
		log.Fatalf("failed to parse form: %s", err)
	}

	username, password, ok := r.BasicAuth()
	log.Printf("User auth: %s %q (%v)", username, password, ok)
	log.Printf("Server records:")
	for k, v := range r.Form {
		log.Printf(" - %q = %q", k, v)
	}
	
	w.WriteHeader(http.StatusOK)
	fmt.Fprintf(w, "OK")
}