Create new ios 14 widget extension cause crashed

Hi, I just create new widget extension on ios 14.
I did not modify anything in my *_widget.swift file, just left it as default after created.
Then I run widget extension to simulator

The result is my extension was crashed, I can not figure out the error and reasons.
I cannot find my widget in the list of widget to add to my home screen

Do you have a boilerplate or point me out what the error is?

I'm using xCode 12 beta.
I found the error detail:
Details
Code Block language
SendProcessControlEvent:toPid: encountered an error: Error Domain=com.apple.dt.deviceprocesscontrolservice Code=8 "Failed to show Widget '*****-widget' error: Error Domain=SBAvocadoDebuggingControllerErrorDomain Code=1 "Failed to get descriptors for extensionBundleID (***-widget)" UserInfo={NSLocalizedDescription=Failed to get descriptors for extensionBundleID (***-widget)}." UserInfo={NSLocalizedDescription=Failed to show Widget '***-widget' error: Error Domain=SBAvocadoDebuggingControllerErrorDomain Code=1 "Failed to get descriptors for extensionBundleID (***-widget)" UserInfo={NSLocalizedDescription=Failed to get descriptors for extensionBundleID (***-widget)}., NSUnderlyingError=0x7fdc7acd2330 {Error Domain=SBAvocadoDebuggingControllerErrorDomain Code=1 "Failed to get descriptors for extensionBundleID (***-widget)" UserInfo={NSLocalizedDescription=Failed to get descriptors for extensionBundleID (*****-widget)}}}
Domain: DTXMessage
Code: 1
--
System Information
macOS Version 10.16 (Build 20A4299v)
Xcode 12.0 (17177)


change to New Build System (Default) might work in this thread:
https://developer.apple.com/forums/thread/651611
I was already on the new build system and have still been getting this error. Do you know if there is any other solution? I have encountered it in every xcode 12 beta (up to beta 5).
Thanks!
Create new ios 14 widget extension cause crashed
 
 
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