client.go
func AcquireRequest() *Request {
	v := requestPool.Get()
	if v == nil {
		return &Request{}
	}
	return v.(*Request)
}
func AcquireRequest() *Request {
	v := requestPool.Get()
	if v == nil {
		return &Request{}
	}
	return v.(*Request)
}
// AcquireRequest returns an empty Request instance from request pool.
//
// The returned Request instance may be passed to ReleaseRequest when it is
// no longer needed. This allows Request recycling, reduces GC pressure
// and usually improves performance.