I had this issue too after installing jdk-12.0.1_windows-x64_bin.zip when trying to use the debugger with IntelliJ IDEA. I was getting an error of (Java HotSpot(TM) 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended). I found, too, going into Setting and search for async and unchecking the Instrumenting agent box. Worked for me!
