httpheader

This is a Go package to parse and generate standard HTTP headers correctly. It knows about complex headers like Accept, Prefer, Link. Unlike many other implementations, it handles all the tricky bits of syntax like quoted commas, multiple header lines, Unicode parameters. It gives you convenient structures to work with, and can serialize them back into HTTP.

This package is distributed under the MIT license, and hosted on GitHub. If it doesn't yet support a header that you need, feel free to open an issue there.

Installation

go get github.com/vfaronov/httpheader

Example

const request = `GET / HTTP/1.1
Host: api.example.com
User-Agent: MyApp/1.2.3 python-requests/2.22.0
Accept: text/*, application/json;q=0.8
Forwarded: for="198.51.100.30:14852";by="[2001:db8::ae:56]";proto=https

`

r, _ := http.ReadRequest(bufio.NewReader(strings.NewReader(request)))

forwarded := httpheader.Forwarded(r.Header)
fmt.Println("received request from user at", forwarded[0].For.IP)

for _, product := range httpheader.UserAgent(r.Header) {
	if product.Name == "MyApp" && product.Version < "2.0" {
		fmt.Println("enabling compatibility mode for", product)
	}
}

accept := httpheader.Accept(r.Header)
acceptJSON := httpheader.MatchAccept(accept, "application/json")
acceptXML := httpheader.MatchAccept(accept, "text/xml")
if acceptXML.Q > acceptJSON.Q {
	fmt.Println("responding with XML")
}

// Output: received request from user at 198.51.100.30
// enabling compatibility mode for {MyApp 1.2.3 }
// responding with XML