goprocess: fix EMFILE error on macOS Catalina (#118)

Limit the number of concurrent goroutines to avoid EMFILE on macOS Catalina.

goprocess/gp.go

@@ -27,6 +27,7 @@ type P struct {
 
 // FindAll returns all the Go processes currently running on this host.
 func FindAll() []P {
+	const concurrencyProcesses = 10 // limit the maximum number of concurrent reading process tasks
 	pss, err := ps.Processes()
 	if err != nil {
 		return nil
@@ -35,10 +36,13 @@ func FindAll() []P {
 	var wg sync.WaitGroup
 	wg.Add(len(pss))
 	found := make(chan P)
+	limitCh := make(chan struct{}, concurrencyProcesses)
 
 	for _, pr := range pss {
+		limitCh <- struct{}{}
 		pr := pr
 		go func() {
+			defer func() { <-limitCh }()
 			defer wg.Done()
 
 			path, version, agent, ok, err := isGo(pr)