fix bug

dbtool/dbtool.go

@@ -74,6 +74,7 @@ func ResultToMap(r *sql.Rows) ([]map[string]interface{}, error) {
 		}
 		for i, v := range vals {
 			tmp[cols[i]] = v
+			vals[i] = nil
 		}
 		result = append(result, tmp)
 	}