move options to a separate file

options.go

@@ -0,0 +1,12 @@
+package sqlmock
+
+import "database/sql/driver"
+
+// ValueConverterOption allows to create a sqlmock connection
+// with a custom ValueConverter to support drivers with special data types.
+func ValueConverterOption(converter driver.ValueConverter) func(*sqlmock) error {
+	return func(s *sqlmock) error {
+		s.converter = converter
+		return nil
+	}
+}