Move to typical go project layout, fix golangci-lint warnings, update deps

vendor/github.com/tklauser/go-sysconf/sysconf_netbsd.go

@@ -25,10 +25,10 @@ const (
 	_POSIX2_UPE       = -1
 )
 
-var clktck struct {
-	sync.Once
-	v int64
-}
+var (
+	clktck     int64
+	clktckOnce sync.Once
+)
 
 func sysconfPOSIX(name int) (int64, error) {
 	// NetBSD does not define all _POSIX_* values used in sysconf_posix.go
@@ -42,6 +42,7 @@ func sysconf(name int) (int64, error) {
 	// Duplicate the relevant values here.
 
 	switch name {
+
 	// 1003.1
 	case SC_ARG_MAX:
 		return sysctl32("kern.argmax"), nil
@@ -54,14 +55,13 @@ func sysconf(name int) (int64, error) {
 		}
 		return -1, nil
 	case SC_CLK_TCK:
-		// TODO: use sync.OnceValue once Go 1.21 is the minimal supported version
-		clktck.Do(func() {
-			clktck.v = -1
+		clktckOnce.Do(func() {
+			clktck = -1
 			if ci, err := unix.SysctlClockinfo("kern.clockrate"); err == nil {
-				clktck.v = int64(ci.Hz)
+				clktck = int64(ci.Hz)
 			}
 		})
-		return clktck.v, nil
+		return clktck, nil
 	case SC_NGROUPS_MAX:
 		return sysctl32("kern.ngroups"), nil
 	case SC_JOB_CONTROL: