Why are r.URL.Host and r.URL.Scheme Empty in My Go Development Server?

Relative URL Access in Development Server

Question:

When running a Go HTTP server in development, why are r.URL.Host and r.URL.Scheme empty for incoming requests?

Answer:

The absence of host and scheme information in r.URL is caused by the use of relative URLs when accessing the server during development. A relative URL does not specify the host or scheme, unlike an absolute URL.

Relative Requests:

Normally, a web browser issues an absolute request, such as:

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

However, when accessing a local development server directly, browsers may use a relative request:

GET / HTTP/1.1
Host: localhost:8080

In this relative request, only the path is specified, and the host and scheme are left out. As a result, r.URL.Host and r.URL.Scheme will be empty when the server receives such a request.

Accessing Host Information:

To retrieve the host information in this situation, you can use the r.Host attribute of the http.Request struct.

host := r.Host

Absolute Requests (Optional):

To ensure that you always receive absolute requests, you can use an HTTP proxy. When using a proxy, the proxy will forward absolute requests to the server, and r.URL.Host and r.URL.Scheme will contain the expected values.

IsAbs() Check:

You can also check whether the URL in the request is absolute or relative using the IsAbs() method of the r.URL struct:

isAbsoluteURL := r.URL.IsAbs()

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