Docker is now available on the official Docker package registry as docker-ce. But before we install docker-ce, we should remove older versions of Docker that may be on our machine:

$ sudo apt remove -y docker docker-engine docker.io

Now, we can install docker-ce:

$ sudo apt install -y docker-ce

Verify if the installation is working by running sudo docker version. You should get an output similar to the following:

$ sudo docker version
Client:
 Version:      18.03.1-ce
 API version:  1.37
 Go version:   go1.9.5
 Git commit:   9ee9f40
 Built:        Thu Apr 26 07:17:38 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm

Server:
 Engine:
  Version:      18.03.1-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.9.5
  Git commit:   9ee9f40
  Built:        Thu Apr 26 07:15:45 2018
  OS/Arch:      linux/amd64
  Experimental: false