使用程序包Azure / go-ntlmssp验证共享点结果401

i have used package like github.com/Azure/go-ntlmssp to authenticate to sharepoint 2010.

url, username, password := "http://www.some-website.com", "admin", "12345"

client := &http.Client{
    Transport: ntlmssp.Negotiator{
        RoundTripper:&http.Transport{},
    },
}

req, _ := http.NewRequest("GET", url, nil)
req.SetBasicAuth(username, password)

res, _ := client.Do(req)

in response i am getting 401 Unauthorized Now here the wierd thing is sometimes(after many trials and not consistent after that also) the authentication happens successfully. And when the authentication fails in response header i can see Www-Authenticate:[NTLM]. Please suggest

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