Golang Select语句范围

Question

In Go, I know that every new enclosing braces declare a new scope, this is true of all control flow statements. Today while writing a program, I stumbled in a scenario where I needed to use the select statement like below

select {
case <-ctx.Done():
    <-ch
    return ctx.Err()
case resp := <-ch:
    var b bytes.Buffer
    if _, err := io.Copy(&b, resp.Body); err != nil {
        return err
    }
}

From the above code, I would like to access the b variable after select statement is closed. Will that be possible?

I know I can move the logic that uses b inside the select, but I would rather not go that route because select is much complicated already on its own and want to keep it slim for easy understanding in future.

Answer 1

It's absolutely fine to declare a var outside the select if it's intended to be used after the select:

var b bytes.Buffer
select {
case <-ctx.Done():
    <-ch
    return ctx.Err()
case resp := <-ch:
    if _, err := io.Copy(&b, resp.Body); err != nil {
        return err
    }
}
... // use b here

There is no shadowing involved here, and you can't shadow unless you have another b declared in an inner scope. An assignment b = <something> inside the select here will just assign to the right b.