Error: No available formula with the name "kubens"

How to install kubens in MacOS? I am trying with Homebrew and getting following error

$ brew install kubens
Error: No available formula with the name "kubens" 
==> Searching for a previously deleted formula (in the last month)...
Warning: homebrew/core is shallow clone. To get complete history run:
  git -C "$(brew --repo homebrew/core)" fetch --unshallow

Error: No previously deleted formula found.
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching taps...
==> Searching taps on GitHub...
Error: No formulae found in taps.