Issue with creating custom provider

I have been trying to make a custom provider but I am having issues. I tried following the Hashicups example provided by Hashicorp but the issue is it runs locally and I am trying to make a provider for something that does not runs locally. To do this I looked up other examples/demos for custom providers and I came across an article by BoxBoat which had an API that was not running locally, what I realized was that I needed a client.go file which was not mentioned in the Hashicups example and I couldn’t find good resources to make thisnclient.go file and I believe that this is what is giving me an error.
So my question is how to create this client.go file and is it necessary for me to build it?
I will attach the image of the error below:

There’s nothing special about the name client.go - you just need whatever code you need to implement the behaviour you need.

As you have not included the custom code which you have written, which is experiencing the error, it is not currently possible for anyone to help you with this.