Fix concurrency limiting?

internal/stopandgo/stopandgo.go

@@ -1,43 +1,31 @@
-// a thing that at least in theory limits concurrency, but i honestly have no clue if it works
 package stopandgo
 
 import (
 	"sync"
-	"sync/atomic"
 )
 
 type StopAndGo struct {
-	wg sync.WaitGroup
+	wg             sync.WaitGroup
 	maxConcurrency int
-	n int32
+	guard          chan struct{}
 }
 
 func NewStopAndGo(max int) *StopAndGo {
 	return &StopAndGo{
 		maxConcurrency: max,
+		guard:          make(chan struct{}, max),
 	}
 }
 
-func (s *StopAndGo) check() {
-	if int(atomic.LoadInt32(&s.n)) >= s.maxConcurrency {
-		s.Wait()
-	}
-}
-
-func (s *StopAndGo) AddN(n int32) {
-	atomic.AddInt32(&s.n, n)
-	s.wg.Add(int(n))
-	// check on a new, separate goroutine so we don't lock everything up
-	go s.check()
-}
 
 func (s *StopAndGo) Add() {
-	s.AddN(1)
+	s.wg.Add(1)
+	s.guard <- struct{}{}
 }
 
-func (s *StopAndGo) Done () {
+func (s *StopAndGo) Done() {
-	atomic.AddInt32(&s.n, -1)
 	s.wg.Done()
+	<-s.guard
 }
 
 func (s *StopAndGo) Wait() {

pkg/goop/clone.go

@@ -24,10 +24,10 @@ import (
 	"time"
 )
 
-const maxConcurrency = 40
+const maxConcurrency = 250
 
 var c = &fasthttp.Client{
-	MaxConnsPerHost: 5000,//utils.MaxInt(maxConcurrency + 250, fasthttp.DefaultMaxConnsPerHost),
+	MaxConnsPerHost: utils.MaxInt(maxConcurrency + 250, fasthttp.DefaultMaxConnsPerHost),
 	TLSConfig: &tls.Config{
 		InsecureSkipVerify: true,
 	},