example run error for async code

[tempbottle]

Problem description
enter the examples dir, and run:
cargo run --example event_write_and_read
then get some error:
Running ~/pravega-client-rust/target/debug/examples/event_write_and_read
thread 'main' panicked at 'Cannot start a runtime from within a runtime. This happens because a function (like block_on) attempted to block the current thread while the thread is being used to drive asynchronous tasks.'

Problem location
there are many async and block_on in the async main function.

Suggestions for an improvement
correct the async and block_on combine in sub-crate or example.

[Tristan1900]

Thanks for the report!
The example should work now.