func (a *Args) Set(key, value string) {
	a.args = setArg(a.args, key, value, argsHasValue)
}
Set sets 'key=value' argument.
package fasthttp
import (
	"bytes"
	"errors"
	"io"
	"sort"
	"sync"
	"github.com/valyala/bytebufferpool"
)
const (
	argsNoValue  = true
	argsHasValue = false
)
func AcquireArgs() *Args {
	return argsPool.Get().(*Args)
}
func ReleaseArgs(a *Args) {
	a.Reset()
	argsPool.Put(a)
}
var argsPool = &sync.Pool{
	New: func() interface{} {
		return &Args{}
	},
}
type Args struct {
	noCopy noCopy
	args []argsKV
	buf  []byte
}
type argsKV struct {
	key     []byte
	value   []byte
	noValue bool
}
func (a *Args) Reset() {
	a.args = a.args[:0]
}
func (a *Args) CopyTo(dst *Args) {
	dst.Reset()
	dst.args = copyArgs(dst.args, a.args)
}
func (a *Args) VisitAll(f func(key, value []byte)) {
	visitArgs(a.args, f)
}
func (a *Args) Len() int {
	return len(a.args)
}
func (a *Args) Parse(s string) {
	a.buf = append(a.buf[:0], s...)
	a.ParseBytes(a.buf)
}
func (a *Args) ParseBytes(b []byte) {
	a.Reset()
	var s argsScanner
	s.b = b
	var kv *argsKV
	a.args, kv = allocArg(a.args)
	for s.next(kv) {
		if len(kv.key) > 0 || len(kv.value) > 0 {
			a.args, kv = allocArg(a.args)
		}
	}
	a.args = releaseArg(a.args)
}
func (a *Args) String() string {
	return string(a.QueryString())
}
func (a *Args) QueryString() []byte {
	a.buf = a.AppendBytes(a.buf[:0])
	return a.buf
}
func (a *Args) Sort(f func(x, y []byte) int) {
	sort.SliceStable(a.args, func(i, j int) bool {
		n := f(a.args[i].key, a.args[j].key)
		if n == 0 {
			return f(a.args[i].value, a.args[j].value) == -1
		}
		return n == -1
	})
}
func (a *Args) AppendBytes(dst []byte) []byte {
	for i, n := 0, len(a.args); i < n; i++ {
		kv := &a.args[i]
		dst = AppendQuotedArg(dst, kv.key)
		if !kv.noValue {
			dst = append(dst, '=')
			if len(kv.value) > 0 {
				dst = AppendQuotedArg(dst, kv.value)
			}
		}
		if i+1 < n {
			dst = append(dst, '&')
		}
	}
	return dst
}
func (a *Args) WriteTo(w io.Writer) (int64, error) {
	n, err := w.Write(a.QueryString())
	return int64(n), err
}
func (a *Args) Del(key string) {
	a.args = delAllArgs(a.args, key)
}
func (a *Args) DelBytes(key []byte) {
	a.args = delAllArgs(a.args, b2s(key))
}
func (a *Args) Add(key, value string) {
	a.args = appendArg(a.args, key, value, argsHasValue)
}
func (a *Args) AddBytesK(key []byte, value string) {
	a.args = appendArg(a.args, b2s(key), value, argsHasValue)
}
func (a *Args) AddBytesV(key string, value []byte) {
	a.args = appendArg(a.args, key, b2s(value), argsHasValue)
}
func (a *Args) AddBytesKV(key, value []byte) {
	a.args = appendArg(a.args, b2s(key), b2s(value), argsHasValue)
}
func (a *Args) AddNoValue(key string) {
	a.args = appendArg(a.args, key, "", argsNoValue)
}
func (a *Args) AddBytesKNoValue(key []byte) {
	a.args = appendArg(a.args, b2s(key), "", argsNoValue)
}