I don't think this issue is linked to the Netty version - it seems you are doing a blocking call at some point, and that's more likely to be the issue.
Did you change anything in the sample code, or just run it without any modification? I might have done an error when copy/pasting the code at some point.
If you have doubts about the Netty versions, I would use the one from Spring Boot, as it's using it far more extensively so you'll reduce the number of potential issues.
I don't think this issue is linked to the Netty version - it seems you are doing a blocking call at some point, and that's more likely to be the issue.
Did you change anything in the sample code, or just run it without any modification? I might have done an error when copy/pasting the code at some point.
If you have doubts about the Netty versions, I would use the one from Spring Boot, as it's using it far more extensively so you'll reduce the number of potential issues.
I haven't modified the code, only I changed boot version to 2.1.8. But it worked as expected on 2.2.0 milestone and snapshot build.