Hi there,
I'm exposing an apex class as REST.

@RestResource(urlMapping='/Opportunity/*')
global with sharing class OpportunityResource {
   @HttpGet
   global static Opportunity doGet() {
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;
        String opportunityId = req.requestURI.substring(req.requestURI.lastIndexOf('/')+1);
        Opportunity result = [select
        Id,
        Account.Id,
        Account.Name,
        Account.Phone,
        Account.Fax,
        Account.Website,
        Account.Type,
        Account.NumberOfEmployees,
        Account.BillingCountry,
        Account.BillingStreet,
        Account.BillingCity,
        Account.BillingState,
        Account.BillingPostalCode,
        Account.Service_Rep_Email__c,
        Account.Industry,
        Account.Special_Contract_Terms__c,
        Account.Billing_Terms__c,
        Account.PEPY__c,
        Number_of_Employees__c,
        Number_of_Sessions__c,
        Product__c,
        Brand__c,
        Benefit_Tier__c,
        Effective_Date__c,
        Number_of_Training_Visits__c,
        Number_of_Trauma_Responses__c,
        Premium_Per_Employee__c
        from Opportunity
        where Id = :opportunityId
        limit 1];
        return result;
    }
    @HttpPost
    global static String doPost(String name,String description) {
        Opportunity opportunity = new Opportunity();
        opportunity.Name = Name;
        opportunity.Description = Description;
        insert opportunity;
        return opportunity.Id;
    }
}

The HTTP Get query works just fine 

curl -X GET \
  https://xxx.lightning.force.com/services/apexrest/Opportunity/0065C0000050OLGQA2 \
  -H 'authorization: Bearer xxx' \
  -H 'cache-control: no-cache' \
  -H 'content-type: application/json' \
  -H 'postman-token: 7ba978b9-f2e8-fd39-b52f-039e5c3d194b' \

But when doing the POST, I don't know why always return
METHOD NOT ALLOWED "GET" Please use POST
 

curl -X POST \
	  https://xxx.force.com/services/apexrest/Opportunity/ \
	  -H 'authorization: Bearer xxx' \
	  -H 'cache-control: no-cache' \
	  -H 'content-type: application/json' \
	  -H 'postman-token: 885fbd88-3171-d7cf-2dfa-7a782a3e5df8' \
	  -d '{
	 "name":"PT ABAL ABAL",
	 "description":"PT Abal"
	}
	'

Any body have an idea why it's happening?
am I missing a configuration or something?
this is pointing to a sandbox lightning.