added some list http header (#17)

* remove unused codes

* added some list http header

header/header.go

@@ -0,0 +1,33 @@
+package header
+
+const (
+	// Headers keys
+	KeyRequestID      = "x-request-id"
+	KeyAuthorization  = "authorization"
+	KeyUserAgent      = "user-agent"
+	KeyContentType    = "content-type"
+	KeyContentAccept  = "accept"
+	KeyAcceptLanguage = "accept-language"
+	KeyCacheControl   = "cache-control"
+
+	// Content type.Specifying the payload in the request
+	ContentTypeJSON = "application/json"
+	ContentTypeXML  = "application/xml"
+	ContentTypeForm = "application/x-www-form-urlencoded"
+
+	// Accepting media. Specifying the types of requested media (in the response)
+	// See here: https://en.wikipedia.org/wiki/Content_negotiation
+	MediaTextPlain = "text/plain"
+	MediaTextHTML  = "text/html"
+	MediaTextCSV   = "text/csv"
+	MediaTextXML   = "text/xml"
+
+	MediaImageGIF  = "image/gif"
+	MediaImageJPEG = "image/jpeg"
+	MediaImagePNG  = "image/png"
+	MediaImageWEBP = "image/webp"
+
+	// Cache control
+	CacheControlNoCache = "no-cache"
+	CacheControlNoStore = "no-store"
+)