With the help of Mohith i got the solution:
Usign ConnectApi.LinkSegmentinput isn´t giving the desired solution:
Code(working with test account hardcoded):
ConnectApi.MessageBodyInput messageInput = new ConnectApi.MessageBodyInput();
messageInput.messageSegments = new List<ConnectApi.MessageSegmentInput>();
ConnectApi.TextSegmentInput textSegment = new ConnectApi.TextSegmentInput();
textSegment.text = 'text ';
messageInput.messageSegments.add(textSegment);
ConnectApi.LinkSegmentinput linksegment = new ConnectApi.LinkSegmentinput();
linksegment.url = 'http://testme.com';
messageInput.messageSegments.add(linksegment);
ConnectApi.FeedItemInput input = new ConnectApi.FeedItemInput();
input.body = messageInput;
ConnectApi.ChatterFeeds.postFeedItem(null, ConnectApi.FeedType.Record, '001g000000FrBWt', input, null);
this is the result:

The desidered solution for me is usign ConnectApi.LinkAttachmentInput:
ConnectApi.FeedItemInput feedItemInput = new ConnectApi.FeedItemInput();
feedItemInput.body = new ConnectApi.MessageBodyInput();
// add the text segment
ConnectApi.TextSegmentInput textSegment = new ConnectApi.TextSegmentInput();
feedItemInput.body.messageSegments = new List<ConnectApi.MessageSegmentInput>();
textSegment.text = 'postText';
feedItemInput.body.messageSegments.add(textSegment);
// add the attachment
ConnectApi.LinkAttachmentInput linkIn = new ConnectApi.LinkAttachmentInput();
linkIn.urlName = 'urlName';
linkIn.url = 'url';
feedItemInput.attachment = linkIn;
ConnectApi.ChatterFeeds.postFeedItem(null, ConnectApi.FeedType.Record, '001g000000FrBWt',feedItemInput, null);