SharePoint Document locked by another user

I am working with SharePoint online. After a user has finished editing and closed the document, SharePoint still locks it down for that user making us not able to interact with the document as we want. I have checked online and i was able to find a solution that suits my need but only works for on-prem sharepoint.

param (
    [string]$url,
    [string]$list,
    [string]$item
)
$w = get-spweb $url
$l = $w.lists[$list]
$i = $l.GetItemById($item)
$s = New-Object Microsoft.SharePoint.SPSite($w.site.id, $i.File.LockedByUser.UserToken)
$w = $s.OpenWeb($w.id)
$l = $w.lists[$list]
$i = $l.GetItemById($item)
$i.File.ReleaseLock($i.File.LockId)

when I modified this for cloud to

param (
    [string]$url,
    [string]$list,
    [string]$item
)
Connect-SPOService -Url https://mysiteurl.com - credential myusername
$w = get-sposite -identity $url
$l = $w.lists[$list]
$i = $l.GetItemById($item)
$s = New-Object Microsoft.SharePoint.SPSite($w.site.id, $i.File.LockedByUser.UserToken)
$w = $s.OpenWeb($w.id)
$l = $w.lists[$list]
$i = $l.GetItemById($item)
$i.File.ReleaseLock($i.File.LockId)

 got an error "cannot index into a null array" at $l = $w.lists[$list] 

Am not good with writing powershell script. What am I doing wrong please?