Why Are Host and Scheme Blank in Go's Development Server HTTP Requests?

Blank Host and Scheme in Development Server for Go

In Go, when utilizing the development server to handle HTTP requests, it's common to encounter an issue where the Host and Scheme properties of the http.Request.URL are blank.

Reason:

When accessing the development server directly (without an HTTP proxy), requests are often made in a relative format:

GET /
Host: localhost:8080

In such cases, the Go HTTP request parser interprets the URL as relative, resulting in empty Host and Scheme properties.

Accessing HTTP Host:

To retrieve the HTTP host from the request, access the Host attribute of the http.Request struct, as seen in the following code:

host := r.Host // Returns the host (e.g., "localhost:8080")

Determining URL Type:

To determine whether a URL is absolute or relative, utilize the IsAbs() method of the URL struct:

isAbsoluteURL := r.URL.IsAbs() // Returns true if the URL is absolute, false otherwise

Example with Netcat:

To test the behavior, create an HTTP request file with the following content:

GET / HTTP/1.1
Host: localhost:8080

And execute the following command:

cat my-http-request-file | nc localhost 8080

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