Why Use an Empty `select` Statement for Blocking in Go's `httptest`?

Why Use an Empty Select Statement in Go?

In the context of net/http/httptest, the purpose of an empty select statement becomes clear. After starting a server using s.Config.Serve(s.Listener), an empty select statement is used to block the execution of the program until the server is closed or an error occurs.

An empty select statement is equivalent to an empty for loop (for {}) in terms of blocking. However, there's a subtle difference in their behavior regarding CPU usage.

Comparison with an Empty For Loop

While both empty select and for loops block forever, they differ in their impact on CPU usage. On most Go architectures, an empty select statement yields the CPU, allowing other processes to execute. In contrast, an empty for loop typically "burns CPU" by spinning at 100% CPU utilization.

Benefits of an Empty Select Statement

Using an empty select statement offers several advantages:

• Blocking without wasting CPU: It allows the program to block until an event occurs without consuming excessive CPU resources.
• Simple and readable: The empty select syntax is concise and straightforward to understand compared to other ways of achieving blocking (e.g., using channels).
• Control over blocking: The select statement provides finer control over blocking compared to an empty for loop, as it allows adding multiple cases to handle different events.

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