background_fetch : Could not determine the dependencies of task ':app:minifyReleaseWithR8'

Your Environment

build app successfully

include background_fetch module. (add background_fetch: ^0.6.0 to pubspec.xml)
insert example code of background_fetch into my main.dart like this: (I didn't do anything except that)

:: import 'package:background_fetch/background_fetch.dart'; ::

void backgroundFetchHeadlessTask(String taskId) async { print('=== [BackgroundFetch] Headless event received.'); BackgroundFetch.finish(taskId); }

Future main() async { :: :: BackgroundFetch.registerHeadlessTask(backgroundFetchHeadlessTask); }

FAILURE: Build failed with an exception.

What went wrong: Could not determine the dependencies of task ':app:minifyReleaseWithR8'.
Could not resolve all task dependencies for configuration ':app:releaseRuntimeClasspath'. Could not find any matches for com.transistorsoft:tsbackgroundfetch:+ as no versions of com.transistorsoft:tsbackgroundfetch are available. Searched in the following locations:
- https://dl.google.com/dl/android/maven2/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- https://jcenter.bintray.com/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- https://storage.googleapis.com/download.flutter.io/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- file:/D:/flutter/CherryTalk/android/app/libs/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- https://repo.maven.apache.org/maven2/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- http://devrepo.kakao.com:8088/nexus/content/groups/public/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml
- https://google.bintray.com/exoplayer/com/transistorsoft/tsbackgroundfetch/maven-metadata.xml Required by: project :app > project :background_fetch
Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
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BUILD FAILED in 31s Running Gradle task 'bundleRelease'... 32.4s Gradle task bundleRelease failed with exit code 1 Process finished with exit code 1

I'd like to know the next step to overcome this failure.