digest files in parallel

parser/parser.go

@@ -11,10 +11,13 @@ import (
 	"os"
 	"os/user"
 	"path/filepath"
+	"runtime"
 	"slices"
 	"strconv"
 	"strings"
+	"sync"
 
+	"golang.org/x/sync/errgroup"
 	"golang.org/x/text/encoding/unicode"
 	"golang.org/x/text/transform"
 
@@ -144,12 +147,25 @@ func fileDigestMap(path string) (map[string]string, error) {
 		files = []string{path}
 	}
 
+	var mu sync.Mutex
+	var g errgroup.Group
+	g.SetLimit(max(runtime.GOMAXPROCS(0)-1, 1))
 	for _, f := range files {
-		digest, err := digestForFile(f)
-		if err != nil {
-			return nil, err
-		}
-		fl[f] = digest
+		g.Go(func() error {
+			digest, err := digestForFile(f)
+			if err != nil {
+				return err
+			}
+
+			mu.Lock()
+			defer mu.Unlock()
+			fl[f] = digest
+			return nil
+		})
+	}
+
+	if err := g.Wait(); err != nil {
+		return nil, err
 	}
 
 	return fl, nil