func NewTokenLimiter(count uint) *TokenLimiter {
	tl := &TokenLimiter{count: count, ch: make(chan *Token, count)}
	for i := uint(0); i < count; i++ {
		tl.ch <- &Token{}
	}
	return tl
}
NewTokenLimiter creates a TokenLimiter with count tokens.
package server
type Token struct {
}
type TokenLimiter struct {
	count uint
	ch    chan *Token
}
func (tl *TokenLimiter) Put(tk *Token) {
	tl.ch <- tk
}
func (tl *TokenLimiter) Get() *Token {
	return <-tl.ch
}