Simplify Client.Do function and lock usage

[byte0o]

1. Simplify the Client.Do function, extract the acquisition of HostClient object into a separate function, and simplify the lock code
2. Remove redundant code from the AcquireReader and AcquireWriter functions of HostClient

[byte0o]

@erikdubbelboer Please help me rerun the test. There is no problem running it in my fork branch. I don't know why there is a problem running the test here.

[Copilot]

Pull Request Overview

This PR refactors the request handling in Client.Do by extracting host lookup and creation into a dedicated helper and streamlines lock usage. It also removes duplicate buffer-initialization branches in HostClient’s reader and writer acquisition methods.

• Extracts hostClient helper to centralize map access and locking
• Moves pendingClientRequests atomic increments into the top-level Do method
• Simplifies AcquireWriter and AcquireReader by consolidating nil-check branches

Comments suppressed due to low confidence (1)

client.go:526

• [nitpick] The helper hostClient retrieves or initializes a HostClient. Renaming it to getHostClient (or similar) could make its intent clearer and align with common getter naming conventions.

func (c *Client) hostClient(host []byte, isTLS bool) (*HostClient, error) {

[erikdubbelboer]

Thanks!