pomerium-cli: add support for a custom browser command (#2617)

internal/authclient/config.go

@@ -2,14 +2,18 @@ package authclient
 
 import (
 	"crypto/tls"
+
+	"github.com/skratchdot/open-golang/open"
 )
 
 type config struct {
+	open      func(rawURL string) error
 	tlsConfig *tls.Config
 }
 
 func getConfig(options ...Option) *config {
 	cfg := new(config)
+	WithBrowserCommand("")(cfg)
 	for _, o := range options {
 		o(cfg)
 	}
@@ -19,6 +23,19 @@ func getConfig(options ...Option) *config {
 // An Option modifies the config.
 type Option func(*config)
 
+// WithBrowserCommand returns an option to configure the browser command.
+func WithBrowserCommand(browserCommand string) Option {
+	return func(cfg *config) {
+		if browserCommand == "" {
+			cfg.open = open.Run
+		} else {
+			cfg.open = func(rawURL string) error {
+				return open.RunWith(rawURL, browserCommand)
+			}
+		}
+	}
+}
+
 // WithTLSConfig returns an option to configure the tls config.
 func WithTLSConfig(tlsConfig *tls.Config) Option {
 	return func(cfg *config) {