How to install ruby on Ubuntu on wsl?

I was trying to install ruby on ubuntu using rvm install "ruby-2.7.0". I was following the instruction on this question https://askubuntu.com/questions/91543/apt-get-update-fails-to-fetch-files-temporary-failure-resolving-error but I am still facing this issue. How can I get this issue resolved.

Err:1 http://security.ubuntu.com/ubuntu focal-security InRelease
      Temporary failure resolving 'security.ubuntu.com'
    Err:2 http://archive.ubuntu.com/ubuntu focal InRelease
      Temporary failure resolving 'archive.ubuntu.com'
    Err:3 http://archive.ubuntu.com/ubuntu focal-updates InRelease
      Temporary failure resolving 'archive.ubuntu.com'
    Err:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease
      Temporary failure resolving 'archive.ubuntu.com'
    Reading package lists... Done
    W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal/InRelease  Temporary failure resolving 'archive.ubuntu.com'
    W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
    W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
    W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/focal-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
    W: Some index files failed to download. They have been ignored, or old ones used instead.
    Reading package lists... Done
    Building dependency tree
    Reading state information... Done
    Calculating upgrade... Done
    The following packages have been kept back:
      ubuntu-advantage-tools
    The following packages will be upgraded:
      initramfs-tools initramfs-tools-bin initramfs-tools-core libssl1.1 openssl sosreport
    6 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
    Need to get 2252 kB of archives.
    After this operation, 4096 B of additional disk space will be used.
    Do you want to continue? [Y/n] n