// SetTrailer sets the trailer metadata that will be sent when an RPC returns.
// It may be called at most once from a unary RPC handler. The ctx is the RPC
// handler's Context or one derived from it.
func SetTrailer(ctx context.Context, md metadata.MD) error {
if md.Len() == 0 {
return nil
}
stream, ok := transport.StreamFromContext(ctx)
if !ok {
return fmt.Errorf("grpc: failed to fetch the stream from the context %v", ctx)
}
return stream.SetTrailer(md)
}
// SendHeader sends header metadata. It may be called at most once from a unary
// RPC handler. The ctx is the RPC handler's Context or one derived from it.
func SendHeader(ctx context.Context, md metadata.MD) error {
if md.Len() == 0 {
return nil
}
stream, ok := transport.StreamFromContext(ctx)
if !ok {
return fmt.Errorf("grpc: failed to fetch the stream from the context %v", ctx)
}
t := stream.ServerTransport()
if t == nil {
grpclog.Fatalf("grpc: SendHeader: %v has no ServerTransport to send header metadata.", stream)
}
return t.WriteHeader(stream, md)
}