How Does Go's `ServeHTTP` Method Work in Custom HTTP Handlers?

Trouble Understanding ServeHTTP - How Does This Code Work?

In Go web development, implementing the ServeHTTP method allows a type to serve as an HTTP handler.

In the example code provided:

type foo int

func (m foo) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "Some text")
}

foo implements the ServeHTTP method, making it an HTTP handler. When http.ListenAndServe is called with foo, the following sequence of events occurs:

• http.ListenAndServe calls srv.ListenAndServe(), which sets up a listener on port 8080.
• When a request is received, l.Accept() creates a connection object (c) which holds the request and response writers (rw).
• c.serve() is launched in a goroutine.
• Within the goroutine, w, err := c.readRequest(ctx) reads the request and creates a response writer object (w).
• serverHandler{...} wraps the ServeHTTP call and ensures a handler is available (either the custom handler or the default multiplexer).
• Finally, handler.ServeHTTP(rw, req) calls the custom ServeHTTP method from foo, which writes "Some text" to the response writer.

In essence, http.ListenAndServe runs a server with the provided handler. When a request is received, the server calls the ServeHTTP method of the handler, which is implemented in foo. This implementation writes the specified text to the response writer, sending it back to the client.

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