Describe your environment
macOS Ventura, otel-cpp 1.8.3

Steps to reproduce
Run the metrics_simple example

What is the expected behavior?
Example should run without error printouts

What is the actual behavior?
During shutdown, the error MetricReader::Collect invoked while Shutdown in progress! is printed.

Additional context
I found this while implementing metrics in a project I work on, but I then discovered that the metrics_simple example does the same.

I’m using a PeriodicExportingMetricReader. An lldb run confirms that PeriodicExportingMetricReader::OnShutDown is being called, but the log message is emitted during the join() call there on the thread. A backtrace shows that OnShutDown is called from MetricReader::Shutdown(), but that doesn’t happen until after MetricReader::shutdown_ is already set to true. If PeriodicExportingMetricReader::OnShutDown does one more call to Collect during the join (which I wouldn’t be surprised if it does), then it’s going to always output that error.