add noOpScanType

dbscan/rowscanner.go

@@ -1,6 +1,7 @@
 package dbscan
 
 import (
+	"database/sql/driver"
 	"fmt"
 	"reflect"
 )
@@ -123,13 +124,23 @@ func startScanner(rs *RowScanner, dstValue reflect.Value) error {
 	)
 }
 
+type noOpScanType struct{}
+
+func (*noOpScanType) Scan(value interface{}) error {
+	return nil
+}
+
+func (noOpScanType) Value() (driver.Value, error) {
+	return nil, nil
+}
+
 func (rs *RowScanner) scanStruct(structValue reflect.Value) error {
 	scans := make([]interface{}, len(rs.columns))
 	for i, column := range rs.columns {
 		fieldIndex, ok := rs.columnToFieldIndex[column]
 		if !ok {
 			if rs.api.allowUnknownColumns {
-				var tmp interface{}
+				var tmp noOpScanType
 				scans[i] = &tmp
 				continue
 			}