displayer.go
func (d *Displayer) ApplyHeaderExtract(header string) error {
	d.RawOutput = d.response.Header.Get(header)
	if d.RawOutput == "" {
		return fmt.Errorf("Response does not contain the '%s' header", header)
	}
	return nil
}
func (d *Displayer) ApplyHeaderExtract(header string) error {
	d.RawOutput = d.response.Header.Get(header)
	if d.RawOutput == "" {
		return fmt.Errorf("Response does not contain the '%s' header", header)
	}
	return nil
}
// ApplyHeaderExtract reads the value of the given header.