code: func ExtractOutgoing(ctx context.Context) NiceMD {
  	md, ok := metadata.FromOutgoingContext(ctx)
  	if !ok {
  		return NiceMD(metadata.Pairs())
  	}
  	return NiceMD(md)
  }
docs: // ExtractOutgoing extracts an outbound metadata from the client-side context.
  //
  // This function always returns a NiceMD wrapper of the metadata.MD, in case the context doesn't have metadata it returns
  // a new empty NiceMD.