我按照文档用 Caddy 进行反向代理，启动caddy后状态一直是failed

[root@VM_0_15_centos _]# service caddy status

Redirecting to /bin/systemctl status caddy.service
● caddy.service - Caddy HTTP/2 web server
   Loaded: loaded (/usr/lib/systemd/system/caddy.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sat 2019-10-19 11:18:13 CST; 2s ago
     Docs: https://caddyserver.com/docs
  Process: 9065 ExecStart=/usr/bin/caddy -conf /etc/caddy/caddy.conf -log stdout -root /tmp -agree (code=exited, status=1/FAILURE)
  Process: 9061 ExecStartPre=/usr/bin/caddy -conf /etc/caddy/caddy.conf -validate (code=exited, status=0/SUCCESS)
 Main PID: 9065 (code=exited, status=1/FAILURE)

Oct 19 11:18:06 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:06 [INFO] [www.liuwena.cn] AuthURL: https://acme-v02.api.letsencrypt.org/acme...41852174
Oct 19 11:18:06 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:06 [INFO] [www.liuwena.cn] acme: use tls-alpn-01 solver
Oct 19 11:18:06 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:06 [INFO] [www.liuwena.cn] acme: Trying to solve TLS-ALPN-01
Oct 19 11:18:08 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:08 http: TLS handshake error from 18.197.227.110:47816: write tcp 172.17.0.15... by peer
Oct 19 11:18:08 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:08 http: TLS handshake error from 66.133.109.36:57584: write tcp 172.17.0.15:... by peer
Oct 19 11:18:13 VM_0_15_centos caddy[9065]: 2019/10/19 11:18:13 [www.liuwena.cn] failed to obtain certificate: acme: Error -> One or more ...problem:
Oct 19 11:18:13 VM_0_15_centos caddy[9065]: [www.liuwena.cn] acme: error: 400 :: urn:ietf:params:acme:error:connection :: Connection reset...er, url:
Oct 19 11:18:13 VM_0_15_centos systemd[1]: caddy.service: main process exited, code=exited, status=1/FAILURE
Oct 19 11:18:13 VM_0_15_centos systemd[1]: Unit caddy.service entered failed state.
Oct 19 11:18:13 VM_0_15_centos systemd[1]: caddy.service failed.
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