modularize monitor, reduce init usage (#81)

* kill process tree using syscall on windows & cleanup (#80)

* kill process tree using syscall on windows & cleanup

* use job api

* add error check for cmd.Start

* modularize monitor, reduce init usage

* replace slices with sort

* update gopsutil & other dependencies

pkg/monitor/conn/conn_fallback.go

@@ -0,0 +1,26 @@
+//go:build !linux
+
+package conn
+
+import (
+	"context"
+	"syscall"
+
+	"github.com/shirou/gopsutil/v4/net"
+)
+
+func GetState(_ context.Context) ([]uint64, error) {
+	var tcpConnCount, udpConnCount uint64
+
+	conns, _ := net.Connections("all")
+	for i := 0; i < len(conns); i++ {
+		switch conns[i].Type {
+		case syscall.SOCK_STREAM:
+			tcpConnCount++
+		case syscall.SOCK_DGRAM:
+			udpConnCount++
+		}
+	}
+
+	return []uint64{tcpConnCount, udpConnCount}, nil
+}

pkg/monitor/conn/conn_linux.go

@@ -0,0 +1,50 @@
+//go:build linux
+
+package conn
+
+import (
+	"context"
+	"syscall"
+
+	"github.com/dean2021/goss"
+	"github.com/shirou/gopsutil/v4/net"
+)
+
+func GetState(_ context.Context) ([]uint64, error) {
+	var tcpConnCount, udpConnCount uint64
+
+	tcpStat, err := goss.ConnectionsWithProtocol(goss.AF_INET, syscall.IPPROTO_TCP)
+	if err == nil {
+		tcpConnCount = uint64(len(tcpStat))
+	}
+
+	udpStat, err := goss.ConnectionsWithProtocol(goss.AF_INET, syscall.IPPROTO_UDP)
+	if err == nil {
+		udpConnCount = uint64(len(udpStat))
+	}
+
+	tcpStat6, err := goss.ConnectionsWithProtocol(goss.AF_INET6, syscall.IPPROTO_TCP)
+	if err == nil {
+		tcpConnCount += uint64(len(tcpStat6))
+	}
+
+	udpStat6, err := goss.ConnectionsWithProtocol(goss.AF_INET6, syscall.IPPROTO_UDP)
+	if err == nil {
+		udpConnCount += uint64(len(udpStat6))
+	}
+
+	if tcpConnCount < 1 && udpConnCount < 1 {
+		// fallback to parsing files
+		conns, _ := net.Connections("all")
+		for _, conn := range conns {
+			switch conn.Type {
+			case syscall.SOCK_STREAM:
+				tcpConnCount++
+			case syscall.SOCK_DGRAM:
+				udpConnCount++
+			}
+		}
+	}
+
+	return []uint64{tcpConnCount, udpConnCount}, nil
+}