我一直在尝试对我的Droplet应用SSL，但是当我尝试执行certbot时，nginx给我一个错误。
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Fri 2018-10-19 13:50:49 UTC; 39s ago
Docs: man:nginx(8)
Process: 18860 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=1/FAILURE)
Process: 18850 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
Oct 19 13:50:47 All-line nginx[18860]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Oct 19 13:50:47 All-line nginx[18860]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Oct 19 13:50:48 All-line nginx[18860]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Oct 19 13:50:48 All-line nginx[18860]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Oct 19 13:50:48 All-line nginx[18860]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Oct 19 13:50:48 All-line nginx[18860]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
Oct 19 13:50:49 All-line nginx[18860]: nginx: [emerg] still could not bind()
Oct 19 13:50:49 All-line systemd[1]: nginx.service: Control process exited, code=exited status=1
Oct 19 13:50:49 All-line systemd[1]: nginx.service: Failed with result 'exit-code'.
Oct 19 13:50:49 All-line systemd[1]: Failed to start A high performance web server and a reverse proxy server.