This is a dirty hard coded hack to show you how to get the outcome your looking for it's not a fully vetted solution. This method will compile a new version of kubectl that will add your needed headers. Maybe it will at least give you a idea to run with.

The reason I wanted to do this is because I put my k8s api endpoint on the internet and safeguarded it with Cloudflare Access. To allow Cloudflare access to let me get past the steel wall I needed to pass in two headers one for my client id and the other for client secret. This ended up working like a charm and is one case someone may want to add custom headers.

Steps:

• I assume you have Go installed and setup, if not go do that now.
• git clone https://github.com/kubernetes/kubernetes.git (could take awhile it's pretty big)
• cd kubernetes/staging/src/k8s.io/client-go/transport/
• Open file round_trippers.go in your favorite code editor
• Search for func (rt userAgentRoundTripper) RoundTrip(req http.Request) (*http.Response, error)
• Add your needed headers by adding lines like this req.Header.Set("Bob-Is", "cool")
• cd back to root folder kubernetes/
• cd cmd/kubectl/
• go build custom-kubectl
• now test it with ./custom-kubectl get ns --v=9
• in that output look for the header you added to the rest calls to K8s api, you should see -H "Bob-Is: cool" in the output
• To make this not a hack maybe see if there's a way to add a kubectl plugin you create do to this for you or ask the kind folks in the k8s community how you can make this hacky method a bit cleaner or if there's a reason adding customer headers isn't a good idea. Worst case parameterize your custom kubectl build to pull in a new parameter you add --custom-request-headers and make it a bit more clean.