Why Are Host and Scheme Attributes Blank in My Go Development Server's Request URL?

Blank Host and Scheme on Development Server

In the initial stages of developing a Go application, using the "hello, world" code to familiarize oneself with the framework is common. However, when attempting to access the Host and Scheme attributes from the request URL, you may encounter unexpected blank values. Why does this occur?

Go's HTTP library parses the raw URL from the request. When you access the server using a relative path, such as:

GET / HTTP/1.1
Host: localhost:8080

The Host and Scheme fields in the URL object remain empty.

In contrast, when accessing the server from a proxy, an absolute URL like this is used:

GET http://localhost:8080/ HTTP/1.1
Host: localhost:8080

This results in the proper population of these fields.

To obtain the HTTP host, consider using the Host attribute of the http.Request struct directly.

Additionally, you can determine the type of URL (relative or absolute) by inspecting the IsAbs() method:

isAbsoluteURL := r.URL.IsAbs()

This check can help distinguish between the two scenarios and guide your code logic accordingly.

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