func (a *Agent) SendFile(filename string, fieldname ...string) *Agent {
	content, err := ioutil.ReadFile(filepath.Clean(filename))
	if err != nil {
		a.errs = append(a.errs, err)
		return a
	}
	ff := AcquireFormFile()
	if len(fieldname) > 0 && fieldname[0] != "" {
		ff.Fieldname = fieldname[0]
	} else {
		ff.Fieldname = "file" + strconv.Itoa(len(a.formFiles)+1)
	}
	ff.Name = filepath.Base(filename)
	ff.Content = append(ff.Content, content...)
	ff.autoRelease = true
	a.formFiles = append(a.formFiles, ff)
	return a
}
SendFile reads file and appends it to multipart form request.
package fiber
import (
	"bytes"
	"crypto/tls"
	"encoding/xml"
	"fmt"
	"io"
	"io/ioutil"
	"mime/multipart"
	"net"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"
	"github.com/gofiber/fiber/v2/internal/go-json"
	"github.com/gofiber/fiber/v2/utils"
	"github.com/valyala/fasthttp"
)
type Request = fasthttp.Request
type Response = fasthttp.Response
type Args = fasthttp.Args
var defaultClient Client
type Client struct {
	UserAgent string
	NoDefaultUserAgentHeader bool
	JSONEncoder utils.JSONMarshal
	JSONDecoder utils.JSONUnmarshal
}
func Get(url string) *Agent { return defaultClient.Get(url) }
func (c *Client) Get(url string) *Agent {
	return c.createAgent(MethodGet, url)
}
func Head(url string) *Agent { return defaultClient.Head(url) }
func (c *Client) Head(url string) *Agent {
	return c.createAgent(MethodHead, url)
}
func Post(url string) *Agent { return defaultClient.Post(url) }
func (c *Client) Post(url string) *Agent {
	return c.createAgent(MethodPost, url)
}
func Put(url string) *Agent { return defaultClient.Put(url) }
func (c *Client) Put(url string) *Agent {
	return c.createAgent(MethodPut, url)
}
func Patch(url string) *Agent { return defaultClient.Patch(url) }
func (c *Client) Patch(url string) *Agent {
	return c.createAgent(MethodPatch, url)
}
func Delete(url string) *Agent { return defaultClient.Delete(url) }
func (c *Client) Delete(url string) *Agent {
	return c.createAgent(MethodDelete, url)
}
func (c *Client) createAgent(method, url string) *Agent {
	a := AcquireAgent()
	a.req.Header.SetMethod(method)
	a.req.SetRequestURI(url)
	a.Name = c.UserAgent
	a.NoDefaultUserAgentHeader = c.NoDefaultUserAgentHeader
	a.jsonDecoder = c.JSONDecoder
	a.jsonEncoder = c.JSONEncoder
	if err := a.Parse(); err != nil {
		a.errs = append(a.errs, err)
	}
	return a
}
type Agent struct {
	Name string
	NoDefaultUserAgentHeader bool
	*fasthttp.HostClient
	req               *Request
	resp              *Response
	dest              []byte
	args              *Args
	timeout           time.Duration
	errs              []error
	formFiles         []*FormFile
	debugWriter       io.Writer
	mw                multipartWriter
	jsonEncoder       utils.JSONMarshal
	jsonDecoder       utils.JSONUnmarshal
	maxRedirectsCount int
	boundary          string
	reuse             bool
	parsed            bool
}
func (a *Agent) Parse() error {
	if a.parsed {
		return nil
	}
	a.parsed = true
	uri := a.req.URI()
	isTLS := false
	scheme := uri.Scheme()
	if bytes.Equal(scheme, strHTTPS) {
		isTLS = true
	} else if !bytes.Equal(scheme, strHTTP) {
		return fmt.Errorf("unsupported protocol %q. http and https are supported", scheme)
	}
	name := a.Name
	if name == "" && !a.NoDefaultUserAgentHeader {
		name = defaultUserAgent
	}
	a.HostClient = &fasthttp.HostClient{
		Addr:                     addMissingPort(string(uri.Host()), isTLS),
		Name:                     name,
		NoDefaultUserAgentHeader: a.NoDefaultUserAgentHeader,
		IsTLS:                    isTLS,
	}
	return nil
}
func addMissingPort(addr string, isTLS bool) string {
	n := strings.Index(addr, ":")
	if n >= 0 {
		return addr
	}
	port := 80
	if isTLS {
		port = 443
	}
	return net.JoinHostPort(addr, strconv.Itoa(port))
}
func (a *Agent) Set(k, v string) *Agent {
	a.req.Header.Set(k, v)
	return a
}
func (a *Agent) SetBytesK(k []byte, v string) *Agent {
	a.req.Header.SetBytesK(k, v)
	return a
}
func (a *Agent) SetBytesV(k string, v []byte) *Agent {
	a.req.Header.SetBytesV(k, v)
	return a
}
func (a *Agent) SetBytesKV(k []byte, v []byte) *Agent {
	a.req.Header.SetBytesKV(k, v)
	return a
}
func (a *Agent) Add(k, v string) *Agent {
	a.req.Header.Add(k, v)
	return a
}
func (a *Agent) AddBytesK(k []byte, v string) *Agent {
	a.req.Header.AddBytesK(k, v)
	return a
}
func (a *Agent) AddBytesV(k string, v []byte) *Agent {
	a.req.Header.AddBytesV(k, v)
	return a
}
func (a *Agent) AddBytesKV(k []byte, v []byte) *Agent {
	a.req.Header.AddBytesKV(k, v)
	return a
}
func (a *Agent) ConnectionClose() *Agent {
	a.req.Header.SetConnectionClose()
	return a
}
func (a *Agent) UserAgent(userAgent string) *Agent {
	a.req.Header.SetUserAgent(userAgent)
	return a
}
func (a *Agent) UserAgentBytes(userAgent []byte) *Agent {
	a.req.Header.SetUserAgentBytes(userAgent)
	return a
}
func (a *Agent) Cookie(key, value string) *Agent {
	a.req.Header.SetCookie(key, value)
	return a
}
func (a *Agent) CookieBytesK(key []byte, value string) *Agent {
	a.req.Header.SetCookieBytesK(key, value)
	return a
}
func (a *Agent) CookieBytesKV(key, value []byte) *Agent {
	a.req.Header.SetCookieBytesKV(key, value)
	return a
}
func (a *Agent) Cookies(kv ...string) *Agent {
	for i := 1; i < len(kv); i += 2 {
		a.req.Header.SetCookie(kv[i-1], kv[i])
	}
	return a
}
func (a *Agent) CookiesBytesKV(kv ...[]byte) *Agent {
	for i := 1; i < len(kv); i += 2 {
		a.req.Header.SetCookieBytesKV(kv[i-1], kv[i])
	}
	return a
}
func (a *Agent) Referer(referer string) *Agent {
	a.req.Header.SetReferer(referer)
	return a
}
func (a *Agent) RefererBytes(referer []byte) *Agent {
	a.req.Header.SetRefererBytes(referer)
	return a
}
func (a *Agent) ContentType(contentType string) *Agent {
	a.req.Header.SetContentType(contentType)
	return a
}
func (a *Agent) ContentTypeBytes(contentType []byte) *Agent {
	a.req.Header.SetContentTypeBytes(contentType)
	return a
}
func (a *Agent) Host(host string) *Agent {
	a.req.URI().SetHost(host)
	return a
}
func (a *Agent) HostBytes(host []byte) *Agent {
	a.req.URI().SetHostBytes(host)
	return a
}
func (a *Agent) QueryString(queryString string) *Agent {
	a.req.URI().SetQueryString(queryString)
	return a
}
func (a *Agent) QueryStringBytes(queryString []byte) *Agent {
	a.req.URI().SetQueryStringBytes(queryString)
	return a
}
func (a *Agent) BasicAuth(username, password string) *Agent {
	a.req.URI().SetUsername(username)
	a.req.URI().SetPassword(password)
	return a
}
func (a *Agent) BasicAuthBytes(username, password []byte) *Agent {
	a.req.URI().SetUsernameBytes(username)
	a.req.URI().SetPasswordBytes(password)
	return a
}
func (a *Agent) BodyString(bodyString string) *Agent {
	a.req.SetBodyString(bodyString)
	return a
}
func (a *Agent) Body(body []byte) *Agent {
	a.req.SetBody(body)
	return a
}
func (a *Agent) BodyStream(bodyStream io.Reader, bodySize int) *Agent {
	a.req.SetBodyStream(bodyStream, bodySize)
	return a
}
func (a *Agent) JSON(v interface{}) *Agent {
	if a.jsonEncoder == nil {
		a.jsonEncoder = json.Marshal
	}
	a.req.Header.SetContentType(MIMEApplicationJSON)
	if body, err := a.jsonEncoder(v); err != nil {
		a.errs = append(a.errs, err)
	} else {
		a.req.SetBody(body)
	}
	return a
}
func (a *Agent) XML(v interface{}) *Agent {
	a.req.Header.SetContentType(MIMEApplicationXML)
	if body, err := xml.Marshal(v); err != nil {
		a.errs = append(a.errs, err)
	} else {
		a.req.SetBody(body)
	}
	return a
}
func (a *Agent) Form(args *Args) *Agent {
	a.req.Header.SetContentType(MIMEApplicationForm)
	if args != nil {
		a.req.SetBody(args.QueryString())
	}
	return a
}
type FormFile struct {
	Fieldname string
	Name string
	Content []byte
	autoRelease bool
}
func (a *Agent) FileData(formFiles ...*FormFile) *Agent {
	a.formFiles = append(a.formFiles, formFiles...)
	return a
}