📝 [Proposal]: Add support to create client from existing client

[goriunov]

Feature Proposal Description

I believe there should be a way to pass custom fasthttp client in to the fiber http client, to allow more granular fine tuning by the users.

Alignment with Express API

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HTTP RFC Standards Compliance

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API Stability

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Feature Examples

Naming can be improved but something along the lines:

cc := client.NewWithFasthttpClien(&fasthttp.Client{...})

### Checklist:

- [X] I agree to follow Fiber's [Code of Conduct](https://github.com/gofiber/fiber/blob/master/.github/CODE_OF_CONDUCT.md).
- [X] I have searched for existing issues that describe my proposal before opening this one.
- [X] I understand that a proposal that does not meet these guidelines may be closed without explanation.

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[gaby]

@efectn Thoughts? Seems reasonable

[luk3skyw4lker]

Couldn't this also be achieved using an option within the existing New method? One option like CustomFastHttpClient or something that when omitted defaults to the internal Fiber fasthttp client. Not sure if this is good but just throwing ideas here

[mitulagr2]

I'll take this if you'd like!

[gaby]

@goriunov You mean a way to override this ? https://github.com/gofiber/fiber/blob/main/client/client.go#L36C2-L36C10