What does the range of channels return? Is the record 'for _, c := range chs' valid?

In Go, the range operator when iterating over a channel returns two values: the first is the value received from the channel, and the second is a boolean indicating whether the channel is open (true if open, false if closed).

However, if you use range in a loop over a channel, for example:

for v := range ch {
    // process v
}

then the loop will receive values from the channel until it is closed. In this case, range returns only the value from the channel, not two values.

Regarding the statement for _, c := range chs, where chs is a slice of channels, yes, such a statement is valid. When iterating over a slice with range, it returns the index and the value. If the index is not needed, it can be replaced with _. For example:

for _, c := range chs {
    // c is a channel from the slice chs
}

Thus, range over a slice of channels returns the index and the channel, and the statement for _, c := range chs is correct.