Fixes: #2

main.go

@@ -158,6 +158,8 @@ func main() {
 }
 
 func run() error {
+	undo := setRlimit()
+	defer undo()
 	maxprocs.Set()
 
 	ctx, cancel := context.WithCancel(context.Background())

rlimit.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix" // syscall package is deprecated
+)
+
+// setRlimit sets the RLIMIT_NOFILE to a higher value.
+// It return a function that you can call to reset the limits to their previous default values.
+// TODO: remove this function once [3] is accepted & implemented.
+//
+// 1. http://0pointer.net/blog/file-descriptor-limits.html
+// 2. https://github.com/systemd/systemd/blob/e7901aba1480db21e06e21cef4f6486ad71b2ec5/src/basic/rlimit-util.c#L373
+// 3. https://github.com/golang/go/issues/46279
+func setRlimit() func() {
+	var targetRlimit uint64 = 512_000 // value taken from link 1 above.
+	var currentRlimit unix.Rlimit
+	var newRlimit unix.Rlimit
+
+	err := unix.Getrlimit(unix.RLIMIT_NOFILE, &currentRlimit)
+	_ = err
+
+	newRlimit.Cur = currentRlimit.Cur
+	newRlimit.Max = currentRlimit.Max
+
+	if newRlimit.Max < targetRlimit {
+		newRlimit.Max = targetRlimit
+	}
+	newRlimit.Cur = newRlimit.Max
+
+	err = unix.Setrlimit(unix.RLIMIT_NOFILE, &newRlimit)
+	_ = err
+
+	undo := func() {
+		err = unix.Setrlimit(unix.RLIMIT_NOFILE, &currentRlimit)
+		_ = err
+	}
+
+	return undo
+}
+
+func printR(r unix.Rlimit) {
+	fmt.Printf("unix.Rlimit{Cur: %d, Max: %d}\n", r.Cur, r.Max)
+}