HTTP中，什么是X-prefix header?
例如 github API 的response headers有很多X前缀的头部:
查一下MDN文档:
Custom proprietary headers have historically been used with an X- prefix, but this convention was deprecated in June 2012 because of the inconveniences it caused when nonstandard fields became standard in RFC 6648; others are listed in an IANA registry, whose original content was defined in RFC 4229. IANA also maintains a registry of proposed new HTTP headers.
原来是自定义头部