func (h MessageHeader) Get(key string) string {
	if h == nil {
		return ""
	}
	v, ok := h[textproto.CanonicalMIMEHeaderKey(key)]
	if ok {
		return v
	}
	return ""
}
Get gets the first value associated with the given key.
package rtsp
import (
	"bytes"
	"net/textproto"
	"strconv"
	"strings"
)
type (
	MessageHeader map[string]string
	Headers map[string]string
	Request struct {
		Verb    string
		Cseq    int
		URI     string
		Auth    string
		Session string
		Header  MessageHeader
	}
	Response struct {
		Proto         string
		Status        string
		StatusCode    int
		ContentLength int64
		Cseq          int
		Header        MessageHeader
		Body          []byte
	}
	Queue map[int]*Request
)
var (
	crnl  = []byte{'\r', '\n'}
	colsp = []byte{':', ' '}
)
func (h MessageHeader) Set(key string, value string) {
	h[textproto.CanonicalMIMEHeaderKey(key)] = value
}