Error verifying clientsecret when refreshing token

[bjaiwu]

Team： When calling refresh_Token does not use the following code： if cliPass, ok := cli.(oauth2.ClientPasswordVerifier); ok { if !cliPass.VerifyPassword(tgr.ClientSecret) { return nil, errors.ErrInvalidClient } }

[cchenggit]

+1

[rp8]

I have a PR #187 that fixed this issue.