showing wrong uptime value

[Abn02]

if windows device uptime is more than 50 days, this code not working and returning wrong uptime.

var (
kernel32DLL = syscall.MustLoadDLL("kernel32")

procGetDiskFreeSpace     = kernel32DLL.MustFindProc("GetDiskFreeSpaceW")
procGetSystemTimes       = kernel32DLL.MustFindProc("GetSystemTimes")
procGetTickCount64       = kernel32DLL.MustFindProc("GetTickCount64")
procGlobalMemoryStatusEx = kernel32DLL.MustFindProc("GlobalMemoryStatusEx")

)

func (u *Uptime) Get() error {
r1, _, e1 := syscall.Syscall(procGetTickCount64.Addr(), 0, 0, 0, 0)
if e1 != 0 {
return error(e1)
}
u.Length = (time.Duration(r1) * time.Millisecond).Seconds()
return nil
}

here if device uptime is more than 50 days (4320000000 milliseconds for 50 days), u.Length value is getting wrong...
can any one please help me to fix this case.