[#19] Add a version with no cdn-sdk deps

Signed-off-by: Pavel Korotkov <pavel@nspcc.ru>

global/context.go

@@ -8,13 +8,16 @@ import (
 )
 
 var (
-	globalContext    context.Context
-	globalContexOnce sync.Once
+	globalContext        context.Context
+	globalContextOnce    sync.Once
+	globalContextBarrier = make(chan struct{})
 )
 
 func Context() context.Context {
-	globalContexOnce.Do(func() {
+	globalContextOnce.Do(func() {
 		globalContext, _ = signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
+		close(globalContextBarrier)
 	})
+	<-globalContextBarrier
 	return globalContext
 }