envelope.go
func (e *Envelope) DeleteHeader(name string) error {
	if name == "" {
		return fmt.Errorf("Provide non-empty header name")
	}

	e.header.Del(name)
	return nil
}
func (e *Envelope) DeleteHeader(name string) error {
	if name == "" {
		return fmt.Errorf("Provide non-empty header name")
	}

	e.header.Del(name)
	return nil
}
// DeleteHeader deletes given header.