fix context usage across codebase

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

broker/context.go

@@ -8,12 +8,18 @@ type brokerKey struct{}
 
 // FromContext returns broker from passed context
 func FromContext(ctx context.Context) (Broker, bool) {
+	if ctx == nil {
+		return nil, false
+	}
 	c, ok := ctx.Value(brokerKey{}).(Broker)
 	return c, ok
 }
 
 // NewContext savess broker in context
 func NewContext(ctx context.Context, s Broker) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
 	return context.WithValue(ctx, brokerKey{}, s)
 }