To quote from the The Go Programming Language Specification:
A "select" statement chooses which of a set of possible communications will proceed. It looks similar to a "switch" statement but with the cases all referring to communication operations.
How can I wait for more than one channel in a case clause, so that only when both channels return the case is executed?
example:
select {
case <-ch1, <-ch2 ... : //wait for ch1 and ch2
// do something
case ..
}
There's no way to wait for multiple channels in the same select case, and there's also no way way to "fallthrough" in select cases, as the documentation describes:
You can easily do something like this via other means, though.
Without select:
This only works if c1 is guaranteed to return despite the availability of c2.
v1 := <-c1
v2 := <-c2
With looping:
This works despite the ordering, but c1 and c2 must only fire once, or it might misbehave:
var v1, v2 int
for i := 0; i < 2; i++ {
select {
case v1 = <-c1:
case v2 = <-c2:
}
}
// both v1 and v2 are set here
With goroutines:
This works either way, but you lose the ordering of results:
c3 := make(chan int, 2)
go func() { c3 <- (<-c1) }()
go func() { c3 <- (<-c2) }()
first := <-c3
second := <-c3
With sync.WaitGroup:
This works either way:
var wg sync.WaitGroup
var v1, v2 int
wg.Add(2)
go func() {
v1 = <-c1
wg.Done()
}()
go func() {
v2 = <-c2
wg.Done()
}()
wg.Wait()
// v1 and v2 are both set
And so on. There are certainly other ways. The best one depends on the details of what you're trying to achieve.