feat(mongox): support nearest read preference

Author: pyshx

mongox/transaction.go

@@ -7,6 +7,7 @@ import (
 	"github.com/reearth/reearthx/usecasex"
 	"go.mongodb.org/mongo-driver/mongo"
 	"go.mongodb.org/mongo-driver/mongo/options"
+	"go.mongodb.org/mongo-driver/mongo/readpref"
 	"go.mongodb.org/mongo-driver/x/mongo/driver"
 )
 
@@ -23,7 +24,13 @@ func NewTransaction(client *mongo.Client) *Transaction {
 }
 
 func (t *Transaction) Begin(ctx context.Context) (usecasex.Tx, error) {
-	s, err := t.client.StartSession(options.Session())
+	// Set the read preference to Nearest
+	rp := readpref.Nearest()
+	
+	// Create session options with the Nearest read preference
+	sessionOpts := options.Session().SetDefaultReadPreference(rp)
+
+	s, err := t.client.StartSession(sessionOpts)
 	if err != nil {
 		return nil, err
 	}