func (rw *ResponseRecorder) Header() http.Header {
	return rw.HeaderMap
}
Header returns the response headers.
package mux
import (
	"bytes"
	"net/http"
	"testing"
)
type ResponseRecorder struct {
	Code      int            
	HeaderMap http.Header    
	Body      *bytes.Buffer  
	Flushed   bool
}
func NewRecorder() *ResponseRecorder {
	return &ResponseRecorder{
		HeaderMap: make(http.Header),
		Body:      new(bytes.Buffer),
	}
}