Why Do Chained Channel Operations in Go\'s `select` Statement Lead to Deadlock?

Chained Channel Operations in a Select Case: Understanding Deadlock

In Go, the fanIn function aggregates values from multiple input channels into a single output channel, providing a form of multiplexing. The select statement in the fanIn function uses non-blocking

However, if the select statement is modified to include chained channel operations, such as:

select {
    case ch <p>strange behavior can occur. Some values may be dropped, leading to a deadlock.</p><p>To understand why this happens, it's essential to remember that in a select statement, only one channel read or write operation is non-blocking. Others behave as if the block operator was used.</p><p>In the modified fanIn function, the first case reads a value from input1 and attempts to write it to ch in a non-blocking manner. This can succeed if the main function consumes the value promptly. However, there's a small chance that the main function loop may not be fast enough to do this.</p><p>In the subsequent iterations of the fanIn loop, the second case is likely to be selected, and by this time, the second goroutine may have written a value to ch. However, if the main function hasn't yet consumed the value from the previous iteration, it will be dropped.</p><p>This cycle of dropping values eventually leads to a situation where there are no more writers, but a reader is still waiting for values, resulting in a deadlock.</p><p>A modified version of the code demonstrates this issue more clearly: https://play.golang.org/p/lcM5OKx09Dj</p>

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