[Bug] Flag -h or --help is not working

[guessi]

Describe the bug
flag -h or --help is not working

instead, it returns,

% kubectl-grep -h
Usage of kubectl-grep:
  -kubeconfig string
    	(optional) absolute path to the kubeconfig file (default "~/.kube/config")

To Reproduce
Steps to reproduce the behavior:

1. kubectl-grep -h or kubectl-grep --help

Expected behavior
It should return default help message, just like kubectl-grep does

Screenshots
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Environment (please complete the following information):
ALL

Additional context
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