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Why is my Go Web Server's Handler Function Called Twice?

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Dec 18, 2024 pm 05:47 PM

Why is my Go Web Server's Handler Function Called Twice?

HandleFunc Invocation Anomaly in Go Web Server

When implementing a simple Go web server to track page visits, the developer encountered a puzzling behavior where the handler function was being called twice. Upon logging the requests, it was discovered that in addition to the expected root route ("/"), the browser was also requesting the favicon.ico file.

Favicon Requests and Handler Function Invocation

An icon file (known as a favicon) provides a small graphical representation of a website and is often displayed in browser tabs and bookmarks. Browsers automatically request favicon.ico for all websites, irrespective of whether one exists or not. If the file is unavailable, browsers typically display a default placeholder image.

In the given example, since the web server did not serve a favicon.ico file, the browser requested it from the root route ("/") as a fallback. The server's HandleFunc was configured to respond to all requests at the root, which resulted in the handler function being called twice (once for the root route and once for the favicon.ico request).

Solution

To resolve this issue, the developer can either create a favicon.ico file and serve it from a dedicated route or explicitly configure the web server to ignore favicon.ico requests.

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