client: Punycode request URL

client.go

@@ -42,7 +42,21 @@ func (c *Client) Get(url string) (*Response, error) {
 
 // Do performs a Gemini request and returns a Gemini response.
 func (c *Client) Do(req *Request) (*Response, error) {
-	// Extract hostname
+	// Punycode request URL
+	if punycode, err := punycodeHost(req.URL.Host); err != nil {
+		return nil, err
+	} else {
+		// Make a copy of the request
+		_req := *req
+		req = &_req
+		_url := *req.URL
+		req.URL = &_url
+
+		// Set the host
+		req.URL.Host = punycode
+	}
+
+	// Extract hostname and punycode it
 	hostname, port, err := net.SplitHostPort(req.Host)
 	if err != nil {
 		return nil, err

punycode.go

@@ -16,6 +16,7 @@ func isASCII(s string) bool {
 	return true
 }
 
+// punycodeHostname returns the punycoded version of hostname.
 func punycodeHostname(hostname string) (string, error) {
 	if net.ParseIP(hostname) != nil {
 		return hostname, nil
@@ -25,3 +26,21 @@ func punycodeHostname(hostname string) (string, error) {
 	}
 	return idna.Lookup.ToASCII(hostname)
 }
+
+// punycodeHost returns the punycoded version of host.
+// host may contain a port.
+func punycodeHost(host string) (string, error) {
+	hostname, port, err := net.SplitHostPort(host)
+	if err != nil {
+		hostname = host
+		port = ""
+	}
+	hostname, err = punycodeHostname(hostname)
+	if err != nil {
+		return "", err
+	}
+	if port == "" {
+		return hostname, nil
+	}
+	return net.JoinHostPort(hostname, port), nil
+}