UnRegister doesn't work as expected for Registry Grouping Example

[shari0311]

While trying to run the example for grouping registries , unregister always returns false.

client_golang/prometheus/registry_test.go

Line 1278 in 3f8bd73

defer globalReg.Unregister(workerReg)

The issue seems to be here , the collectorID is not present in the globalRegistry so it always returns false
if _, exists := r.collectorsByID[collectorID]; !exists { r.mtx.RUnlock() return false }

go_version: 1.14 & 1.17