1 files changed, 11 insertions, 0 deletions
diff --git a/internal/database/db.go b/internal/database/db.go
index 2fbfe74..d5aa1f4 100644
--- a/internal/database/db.go
+++ b/internal/database/db.go
@@ -11,11 +11,13 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"sync"
 )
 
 type DB struct {
 	fp    *os.File
 	cache map[string]struct{}
+	mu    *sync.RWMutex
 }
 
 func New(path string) (*DB, error) {
@@ -28,6 +30,7 @@ func New(path string) (*DB, error) {
 	db := &DB{
 		fp:    fp,
 		cache: map[string]struct{}{},
+		mu:    &sync.RWMutex{},
 	}
 	for part := range bytes.SplitSeq(cache, []byte("\n")) {
 		db.cache[string(part)] = struct{}{}
@@ -41,14 +44,22 @@ func (d *DB) Close() error {
 }
 
 func (d *DB) Exists(s string) bool {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+
 	_, ok := d.cache[s]
 	return ok
 }
 
 func (d *DB) Append(s string) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
 	if d.Exists(s) {
 		return nil
 	}
+
+	d.cache[s] = struct{}{}
 	_, err := fmt.Fprintln(d.fp, s)
 	return err
 }