func (t kind) Build(reason Reason, format string) Factory {
	return &factory{code: int(t), reason: reason, format: format}
}
Build builds a factory to generate errors with predefined format.
package errors
type Builder interface {
	Build(reason Reason, format string) Factory
	Error(format string, v ...interface{}) error
}
type kind int
func newKind(code int) Builder {
	return kind(code)
}