Unable to assign licence to user

Hello!

Following the example here I am trying to assing a licence to an user in Azure AD. I created the following dummy script to illustrate my problem:

package main

import (
	"context"
	"log"

	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
	"github.com/google/uuid"
	msgraphsdk "github.com/microsoftgraph/msgraph-sdk-go"
	graphmodels "github.com/microsoftgraph/msgraph-sdk-go/models"
	graphusers "github.com/microsoftgraph/msgraph-sdk-go/users"
)

func main() {
	// For testing fill the values here
	tenantID := "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
	clientID := "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
	clientSecret := "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
	userID := "02a83423-br0c-4376-93a8-ed405936e0e6" // I made this up for creating the issue
	licenceSKUID := "e8b967fb-3c0c-4ba7-225e-f857999a9d30_f30db741-07e9-47e9-999c-80727f46fr8f" // This as well

	// Authenticate with Azure AD and create a Graph client
	cred, err := azidentity.NewClientSecretCredential(tenantID, clientID, clientSecret, nil)
	if err != nil {
		log.Fatal(err)
	}
	graphClient, err := msgraphsdk.NewGraphServiceClientWithCredentials(
		cred,
		[]string{"https://graph.microsoft.com/.default"},
	)
	if err != nil {
		log.Fatal(err)
	}

	// Look for the user to make sure the UUID is correct
	u, err := graphClient.Users().ByUserIdString(userID).Get(context.Background(), nil)
	if err != nil {
		log.Fatal(err)
	}
	username := *u.GetDisplayName()
	log.Printf("User %s found", username)

	// Look for the license to make sure the UUID is correct
	l, err := graphClient.SubscribedSkus().BySubscribedSkuIdString(licenceSKUID).Get(context.Background(), nil)
	if err != nil {
		log.Fatal(err)
	}
	skuID := l.GetSkuId()
	licenceName := *l.GetSkuPartNumber()
	log.Printf("License %s found", licenceName)
	log.Printf("Assigning license %s to user %s", licenceName, username)

	// Assign the license to the user according to the documentation
	requestBody := graphusers.NewItemAssignLicensePostRequestBody()

	assignedLicense := graphmodels.NewAssignedLicense()
	disabledPlans := []uuid.UUID{}
	assignedLicense.SetDisabledPlans(disabledPlans)
	assignedLicense.SetSkuId(skuID)
	addLicenses := []graphmodels.AssignedLicenseable{
		assignedLicense,
	}
	requestBody.SetAddLicenses(addLicenses)
	removeLicenses := []uuid.UUID{}
	requestBody.SetRemoveLicenses(removeLicenses)
	assignLicense, err := graphClient.Users().ByUserIdString(userID).AssignLicense().Post(context.Background(), requestBody, nil)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("%v", assignLicense.GetAssignedLicenses())
}

So to make sure I only pass existing IDs to the licence assignment code, I use the same graph client to get the objects before. After running it, the logs are:

2023/09/08 16:25:02 User Test User found
2023/09/08 16:25:02 License FLOW_FREE found
2023/09/08 16:25:02 Assigning license FLOW_FREE to user Test User
2023/09/08 16:25:03 error status code received from the API
exit status 1

I made sure the client being used has the appropriate permissions:

Given the very vague error message I can not really debug any further on the issue. I tried to use a debugger to look at the error but the values are strange:

err.(*odataerrors.ODataError).ApiError.Message = ""
err.(*odataerrors.ODataError).ApiError.ResponseStatusCode = 0
err.(*odataerrors.ODataError).ApiError.ResponseHeaders.header.headers = map[string]map[string]struct {} []

As a side note (maybe it its of importance). I am using the "long" version of the licence ID in the code (<TENANT_ID>_<SKU_ID>) because if I don't then this line

l, err := graphClient.SubscribedSkus().BySubscribedSkuIdString(licenceSKUID).Get(context.Background(), nil)

will be the one failing with a similar error (also empty message and status code 0)

I would appreciate some help, because a response code of 0 seems to be me like an indication of something bigger being wrong. It could also be that the documentation is not correct.

Versions

I am using the following library versions:

github.com/google/uuid v1.3.1
github.com/microsoftgraph/msgraph-sdk-go v1.17.0

Start by reproducing the provided Go example, focusing on the SubscribedSkus().BySubscribedSkuIdString(...).Get and Users().ByUserIdString(...).AssignLicense().Post entry points. Compare the returned errors and API responses to determine whether the status-0 error comes from the SDK or Microsoft Graph, then document a reproducible cause and actionable resolution.