You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: core.go
    path of file: ./repos/fiber/client
    
    the code of the file until where you have to start completion: package client

import (
	"context"
	"errors"
	"net"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"

	"github.com/gofiber/fiber/v3"
	"github.com/gofiber/fiber/v3/addon/retry"
	"github.com/valyala/fasthttp"
)

var bou
    
func (c *core) execFunc() (*Response, error) {
	resp := AcquireResponse()
	resp.setClient(c.client)
	resp.setRequest(c.req)

	// To avoid memory allocation reuse of data structures such as errch.
	done := int32(0)
	errCh, reqv := acquireErrChan(), fasthttp.AcquireRequest()
	defer func() {
		releaseErrChan(errCh)
	}()

	c.req.RawRequest.CopyTo(reqv)
	cfg := c.getRetryConfig()

	var err error
	go func() {
		respv := fasthttp.AcquireResponse()
		defer func() {
			fasthttp.ReleaseRequest(reqv)
			fasthttp.ReleaseResponse(respv)
		}()

		if cfg != nil {
			err = retry.NewExponentialBackoff(*cfg).Retry(func() error {
				if c.req.maxRedirects > 0 && (string(reqv.Header.Method()) == fiber.MethodGet || string(reqv.Header.Method()) == fiber.MethodHead) {
					return c.client.fasthttp.DoRedirects(reqv, respv, c.req.maxRedirects)
				}

				return c.client.fasthttp.Do(reqv, respv)
			})
		} else {
			if c.req.maxRedirects > 0 && (string(reqv.Header.Method()) == fiber.MethodGet || string(reqv.Header.Method()) == fiber.MethodHead) {
				err = c.client.fasthttp.DoRedirects(reqv, respv, c.req.maxRedirects)
			} else {
				err = c.client.fasthttp.Do(reqv, respv)
			}
		}

		if atomic.CompareAndSwapInt32(&done, 0, 1) {
			if err != nil {
				errCh <- err
				return
			}
			respv.CopyTo(resp.RawResponse)
			errCh <- nil
		}
	}()

	select {
	case err := <-errCh:
		if err != nil {
			// When get error should release Response
			ReleaseResponse(resp)
			return nil, err
		}
		return resp, nil
	case <-c.ctx.Done():
		atomic.SwapInt32(&done, 1)
		ReleaseResponse(resp)
		return nil, ErrTimeoutOrCancel
	}
}