caddy: Infinite Redirect with Caddy 0.9.3

1. What version of Caddy are you running (caddy -version)?

Caddy 0.9.3

2. What are you trying to do?

Serve https with automatic SSL

3. What is your entire Caddyfile?

https://sub.domain.com

log stdout
prometheus 0.0.0.0:9180

tls user@domain.com

proxy / upstream:80 {
  transparent
}

4. How did you run Caddy (give the full command and describe the execution environment)?

docker run -d --link upstream -p 0.0.0.0:80:80 -p 0.0.0.0:443:443 my-caddy-image

5. What did you expect to see?

The content of https://sub.domain.com/

6. What did you see instead (give full error messages and/or log)?

Infinite redirects from https://sub.domain.com/ to https://sub.domain.com/

7. How can someone who is starting from scratch reproduce this behavior as minimally as possible?

Use this Dockerfile:

FROM alpine:3.4
RUN apk --update --no-cache add \
  ca-certificates \
  curl \
  git \
  openssh-client \
  && rm -rf /var/cache/apk/*
RUN mkdir -p /bin /srv
RUN curl -fsSL "https://caddyserver.com/download/build?os=linux&arch=amd64&features=cors%2Cgit%2Chugo%2Cminify%2Cprometheus%2Cratelimit%2Crealip%2Csearch%2Ccloudflare%2Cgooglecloud%2Croute53" -o /tmp/caddy.tar.gz \
  && cd /tmp \
  && tar xvzf caddy.tar.gz \
  && mv /tmp/caddy /bin/caddy \
  && rm -rf /tmp/caddy.tar.gz
VOLUME [ "/srv" ]
WORKDIR /srv
ADD Caddyfile /Caddyfile
EXPOSE 80 443 9180
CMD [ "/bin/caddy", "-http2=false" ]

and the above Caddyfile, run:

docker build -t my-caddy-image .
docker run -d -p 0.0.0.0:80:80 -p 0.0.0.0:443:443 my-caddy-image