I encountered the same problem as well. I was installing a fixed version using chef and the problem was exactly as the OP has.
To solve it, I searched for the available packages
apt-cache madison docker-ce
It gave me an output like this
docker-ce | 18.06.1~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
docker-ce | 18.06.0~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
docker-ce | 18.03.1~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
W: Target Packages (stable/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/Docker.list:1 and /etc/apt/sources.list.d/docker-stable.list:1
…
And I picked most up-to-date version from the list and it worked.
