如何在Go中以相同的方式对来自多个通道的输入做出反应？

Question

I have some concurrent code that has two different timeout intervals, one static and one dynamic. I want to react the same way to both of them. This is the gist of it:

select {
case <-time.After(staticTimeoutInterval):
    doSomething()
case <-time.After(dynamicTimeoutInterval):
    doSomething()
}

Is there any way to write doSomething() only once? It's strange that select isn't as flexible as switch in this respect.

Answer 1

In your specific case you can use something like

timeout := min(staticTimeoutInterval, dynamicTimeoutInterval)

select {
case <-time.After(timeout):
    doSomething()
}

func min(a, b time.Duration) int {
    if a < b {
        return a
    }
    return b
}

About the seemingly inconsistent treatment of switch and select - while these statements have similar syntax, the purpose of switch is branched execution, while the purpose of select is communication.

If I can exaggerate:

• switch is about the part after the case expression - the case expression here is mostly a simple, side-effect free expression
• select is about the part in the case expression - the case expression here provides you with the important communication side effect and is not trivial to implement at all

Allowing fallthrough in select will allow you to save a couple of lines in some cases, but it will often make select statements harder to reason about. Given a similar choice in other situations, the Go creators have almost always gone with more verbose but simpler to understand.