Added some NIP-42 functionality to the client (relay.go) (#38)

README.md

@@ -87,6 +87,46 @@ for _, url := range []string{"wss://nostr.zebedee.cloud", "wss://nostr-pub.wello
 }
 ```
 
+### Authenticating with NIP-42
+
+For this section, the user needs access to a relay implementing NIP-42.
+E.g., https://github.com/fiatjaf/relayer with a relay implementing the relayer.Auther interface.
+
+``` go
+func main() {
+	url := "ws://localhost:7447"
+
+	// Once the connection is initiated the server will send "AUTH" with the challenge string.
+	relay, err := nostr.RelayConnect(context.Background(), url)
+	if err != nil {
+		panic(err)
+	}
+
+	// Initialize test user.
+	sk := nostr.GeneratePrivateKey()
+	pub, _ := nostr.GetPublicKey(sk)
+	npub, _ := nip19.EncodePublicKey(pub)
+
+	// Relay.Challenges channel will receive the "AUTH" command.
+	challenge := <-relay.Challenges
+
+	// Create the auth event to send back.
+	// The user will be authenticated as pub.
+	event := nip42.CreateUnsignedAuthEvent(challenge, pub, url)
+	event.Sign(sk)
+
+	// Set-up context with 3 second time out.
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	// Send the event by calling relay.Auth.
+	// Returned status is either success, fail, or sent (if no reply given in the 3 second timeout).
+	auth_status := relay.Auth(ctx, event)
+
+	fmt.Printf("authenticated as %s: %s\n", npub, auth_status)
+}
+```
+
 ### Example script
 
 ```