adopt latest golang enhancements (#91)

pkg/es/role.go

@@ -20,6 +20,8 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
+	"maps"
+	"slices"
 
 	"codeberg.org/scip/esctl/pkg/cfg"
 	"codeberg.org/scip/esctl/pkg/printer"
@@ -33,15 +35,7 @@ func RoleNames(conf *cfg.Config) ([]string, error) {
 		return nil, fmt.Errorf("failed to get roles: %w", esErrorString(err))
 	}
 
-	roles := make([]string, len(res))
-
-	idx := 0
-	for name := range res {
-		roles[idx] = name
-		idx++
-	}
-
-	return roles, nil
+	return slices.Collect(maps.Keys(res)), nil
 }
 
 func RoleList(conf *cfg.Config) error {