// SetTrailer sets the trailer metadata which will be sent with the RPC status
// by the server. This can only be called at most once. Server side only.
func (s *Stream) SetTrailer(md metadata.MD) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.trailer != nil {
return ErrIllegalTrailerSet
}
s.trailer = md.Copy()
return nil
}
