func PlayAll() {
	for _, source := range pool.playing {
		source.Play()
	}
}
PlayAll will play all sources
package openal
import (
	"sync"
	"time"
	"github.com/tanema/amore/audio/openal/al"
)
const maxSources = 64
var pool *audioPool
type audioPool struct {
	mutex        sync.Mutex
	totalSources int
	sources      [maxSources]al.Source
	available    []al.Source
	playing      map[al.Source]*Source
}
func init() {
	if err := al.OpenDevice(); err != nil {
		panic(err)
	}
}
func GetVolume() float32 { return al.ListenerGain() }
func SetVolume(gain float32) {
	al.SetListenerGain(gain)
}
func PauseAll() {
	for _, source := range pool.playing {
		source.Pause()
	}
}