implements Host.Uptime on windows

host_windows.go

@@ -4,6 +4,7 @@ package main
 
 import (
 	"os"
+	"syscall"
 )
 
 func (h Host) HostInfo() (HostInfo, error) {
@@ -15,5 +16,15 @@ func (h Host) HostInfo() (HostInfo, error) {
 
 	ret.Hostname = hostname
 
+	kernel32, err := syscall.LoadLibrary("kernel32.dll")
+	if err != nil {
+		return ret, err
+	}
+	defer syscall.FreeLibrary(kernel32)
+	GetTickCount, _ := syscall.GetProcAddress(kernel32, "GetTickCount")
+
+	uptimemsec, _, err := syscall.Syscall(uintptr(GetTickCount), 0, 0, 0, 0)
+
+	ret.Uptime = int64(uptimemsec) / 1000
 	return ret, nil
 }