I am using this code to call a REST API inside my same domain
HttpResponse res = new HttpResponse();
Http http = new Http();
req.setEndpoint('https://chaarvim-dev-ed.my.salesforce.com/services/data/v48.0/composite/tree/Account/');
req.setMethod('POST');
req.setCompressed(false);
req.setBody(strRequest);
req.setHeader('Content-Type', 'application/json');
req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
try {
res = http.send(req);
} catch(System.CalloutException e) {
System.debug('Callout error: '+ e);
}
But i am getting
[{"message":"This session is not valid for use with the REST API","errorCode":"INVALID_SESSION_ID"}]
Any Suggestions please.