Add method to validate configuration

cmd/command.go

@@ -1,6 +1,7 @@
 package lumecmd
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"strconv"
@@ -92,3 +93,12 @@ func GetCommand(name string) (Command, bool) {
 	cmd, ok := commandRegistry[name]
 	return cmd, ok
 }
+
+// Validate configuration struct
+func (c *Config) Validate() error {
+	var err error
+	if c.AccessToken == "" {
+		err = errors.New("access_token is not set")
+	}
+	return err
+}

cmd/main.go

@@ -33,9 +33,8 @@ func Main(args []string) (int, error) {
 		config.AccessToken = envAccessToken
 	}
 
-	if config.AccessToken == "" {
-		err = errors.New("fatal: access token is not set")
-		return ExitError, err
+	if err = config.Validate(); err != nil {
+		return ExitError, fmt.Errorf("fatal: %s", err)
 	}
 
 	flag.Parse()