fix context usage across codebase

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

micro.go

@@ -83,12 +83,18 @@ func NewService(opts ...Option) Service {
 
 // FromContext retrieves a Service from the Context.
 func FromContext(ctx context.Context) (Service, bool) {
+	if ctx == nil {
+		return nil, false
+	}
 	s, ok := ctx.Value(serviceKey{}).(Service)
 	return s, ok
 }
 
 // NewContext returns a new Context with the Service embedded within it.
 func NewContext(ctx context.Context, s Service) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
 	return context.WithValue(ctx, serviceKey{}, s)
 }