Instead of requiring callers to read the struct fields to check for an
error, provide the exit results via a function instead which is more
natural.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
In all of the examples, its recommended to call `Wait()` before starting
a process/task.
Since `Wait()` is a blocking call, this means it must be called from a
goroutine like so:
```go
statusC := make(chan uint32)
go func() {
status, err := task.Wait(ctx)
if err != nil {
// handle async err
}
statusC <- status
}()
task.Start(ctx)
<-statusC
```
This means there is a race here where there is no guarentee when the
goroutine is going to be scheduled, and even a bit more since this
requires an RPC call to be made.
In addition, this code is very messy and a common pattern for any caller
using Wait+Start.
Instead, this changes `Wait()` to use an async model having `Wait()`
return a channel instead of the code itself.
This ensures that when `Wait()` returns that the client has a handle on
the event stream (already made the RPC request) before returning and
reduces any sort of race to how the stream is handled by grpc since we
can't guarentee that we have a goroutine running and blocked on
`Recv()`.
Making `Wait()` async also cleans up the code in the caller drastically:
```go
statusC, err := task.Wait(ctx)
if err != nil {
return err
}
task.Start(ctx)
status := <-statusC
if status.Err != nil {
return err
}
```
No more spinning up goroutines and more natural error
handling for the caller.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
The syscall package is locked down and the comment in [1] advises to
switch code to use the corresponding package from golang.org/x/sys. Do
so and replace usage of package syscall with package
golang.org/x/sys/{unix,windows} where applicable.
[1] https://github.com/golang/go/blob/master/src/syscall/syscall.go#L21-L24
This will also allow to get updates and fixes for syscall wrappers
without having to use a new go version.
Errno, Signal and SysProcAttr aren't changed as they haven't been
implemented in x/sys/. Stat_t from syscall is used if standard library
packages (e.g. os) require it. syscall.ENOTSUP, syscall.SIGKILL and
syscall.SIGTERM are used for cross-platform files.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
