monasca grafana use https keystone failed

[like-inspur]

I use external keystone with https for monasca authentication, when I config it for monasca grafana, but I found that grafana always outputs error and authenticates failed like this:
t=2019-05-08T07:23:18+0000 lvl=eror msg="Error while trying to authenticate user" logger=context userId=0 orgId=0 uname= error="Post https://10.200.0.50:5000/v3/auth/tokens: x509: certificate signed by unknown authority"
t=2019-05-08T07:23:18+0000 lvl=eror msg="Request Completed" logger=context userId=0 orgId=0 uname= method=POST path=/login status=500 remote_addr=172.31.72.243 time_ms=13ns size=53

My config of grafana config is like this:
[auth.keystone]
enabled = true
verify_ssl_cert = false
v3 = true
default_domain = Default