Unable to ssh into docker playground virtual machine (Permission denied (publickey) error)

Docker playground is a very useful place to learn how to use docker. However, the web interface is sometimes can be quite difficult to use, especially if we are trying to copy long commands into the virtual machine. 

A good solution to this, is to connect to the virtual machine using ssh. We can copy the link at the ssh column of the virtual machine, and paste it in our terminal. 

One of the issue that we encounter when we are trying to ssh into the virtual machine, is we will get permission denied (publickey) error, like below 

The reason this happened is, the ssh server inside the playground's virtual machine is expecting the client to connect from a machine that owns a ed25519 key. This can be verified by running below command inside the playground's virtual machine

To encounter that, simply create an ed25519 in our machine, using ssh-keygen

$ ssh-keygen -t ed25519

We should be able to ssh into the playground's virtual machine now