Install Docker on WSL Ubuntu 18.04

(2020.3.29) It is difficult to introduce Docker on WSL in the first place. WSL2 scheduled to be released in May 2020 can introduce Docker without problems, so it is good to use it after May.

~~ ## [Overview] Install Docker on WSL Ubuntu18.04 lts. ~~

~~ ## [Environment / Version] ・ OS: WSL Ubuntu 18.04 ・ Arch: amd64 ・ Docker version: 19.03.8 ~~

~~ ## [Introduction procedure] ~~

~~ ① Update the apt package list ~~

~~``` sudo apt-get update

 ~~ ② Install the package ~~

~~ sudo apt-get install -y \
  > apt-transport-https \
  > ca-certificates \
  > software-properties-common ~~


 ~~ ③ Add Docker's GPG key ~~

~~```
$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

OK
```~~

 ~~ If the input is correct, OK will be displayed. ~~


 ~~ ④ Add repository ~~

$ sudo add-apt-repository \

"deb [arch=amd64] https://download.docker.com/linux/ubuntu
$(lsb_release -cs)
"stable"

 ~~ * The amd64 part of [arch = amd64] depends on the Linux architecture you are using. You can check the architecture with the arch command ~~

 ~~ We will update apt once the repository is added. ~~

$ sudo apt-get update

 ~~ Now you are ready to install Docker. ~~


 ~~ ⑤ Install Docker ~~

$ sudo apt-get install docker-ce

 ~~ After installation, check the Docker version with the following command. ~~

~~```
$ docker version
```~~

 ~~ Then ... ~~

~~```
Client: Docker Engine - Community
 Version:           19.03.8
 API version:       1.40
 Go version:        go1.12.17
 Git commit:        afacb8b7f0
 Built:             Wed Mar 11 01:25:46 2020
 OS/Arch:           linux/amd64
 Experimental:      false
 Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
```~~

 ~~ You have successfully installed. However, as far as I can see the error message in the two lines below, it seems that Docker has not started yet. This issue will be resolved in another entry. ~~

 ~~ ## [Reference] ~~

 ~~ [Docker Textbook for Programmers 2nd Edition] ~~~~ (https://www.amazon.co.jp/%E3%83%97%E3%83%AD%E3%82%B0% E3% 83% A9% E3% 83% 9E% E3% 81% AE% E3% 81% 9F% E3% 82% 81% E3% 81% AEDocker% E6% 95% 99% E7% A7% 91% E6% 9B% B8-% E7% AC% AC2% E7% 89% 88-% E3% 82% A4% E3% 83% B3% E3% 83% 95% E3% 83% A9% E3% 81% AE% E5% 9F% BA% E7% A4% 8E% E7% 9F% A5% E8% AD% 98-% E3% 82% B3% E3% 83% BC% E3% 83% 89% E3% 81% AB% E3% 82 % 88% E3% 82% 8B% E7% 92% B0% E5% A2% 83% E6% A7% 8B% E7% AF% 89% E3% 81% AE% E8% 87% AA% E5% 8B% 95 % E5% 8C% 96-WINGS% E3% 83% 97% E3% 83% AD% E3% 82% B8% E3% 82% A7% E3% 82% AF% E3% 83% 88 / dp / 4798153222 / ref = pd_sbs_14_t_0 / 357-5789801-8277315? _encoding = UTF8 & pd_rd_i = 4798153222 & pd_rd_r = 966c4f81-1911-4e67-8b9b-005338dea134 & pd_rd_w = P1ktL & pd_rd_wg = FhRzp & pf_rd_p = ca22fd73-0f1e-4b39-9917-c84a20b3f3a8 & pf_rd_r = 0BDCYKXWMJ9T9HDAXM43 & psc = 1 & refRID = 0BDCYKXWMJ9T9HDAXM43) ~~

~~https://qiita.com/soumi/items/5b01d88c187b678c0474~~