Authentication fails with 401

[vk18vk]

Authentication fails while using package for NTLM authentication. But the strange thing here is authentication do passes sometimes after many requests. Say for example after 5 or 10 requests, that means authentication happens at random trials.
Is there anything to be changed from client end

[ivandeex]

This happened for us if go-ntlmssp is used from several goroutines. See rclone/rclone#2921 (comment). We solved this by guarding Negotiator.RoundTrip calls with a mutex.