GCP華僑（digdag keyの設定方法について）

digdagシェル

_export:
  bq:
    dataset: プロジェクトID

+step1:
  bq>:
    data: "SELECT * FROM `プロジェクトID.データベース名.テーブル名`"

上記digdagシェルをLinux(Debian GNU/Linux 9)から実行したところ下記のエラーが出力されました

$ sudo digdag run auto-test.dig 
2020-02-19 06:56:13 +0000: Digdag v0.9.41
2020-02-19 06:56:15 +0000 [WARN] (main): Reusing the last session time 2020-02-19T00:00:00+00:00.
2020-02-19 06:56:15 +0000 [INFO] (main): Using session /home/wvp360gqanukcqhg/test/.digdag/status/20200219T000000+0000.
2020-02-19 06:56:15 +0000 [INFO] (main): Starting a new session project id=1 workflow name=auto-test session_time=2020-02-19T00:00:00+00:00
2020-02-19 06:56:18 +0000 [INFO] (0016@[0:default]+auto-test+step1): bq>: {data=SELECT * FROM `dotted-embassy-266410.oraclebronze_1.table_1`}
2020-02-19 06:56:18 +0000 [ERROR] (0016@[0:default]+auto-test+step1): Task failed with unexpected error: Secret not found for key: 'gcp.crede
ntial'
io.digdag.spi.SecretNotFoundException: Secret not found for key: 'gcp.credential'
        at io.digdag.spi.SecretProvider.lambda$getSecret$0(SecretProvider.java:21)
        at com.google.common.base.Absent.or(Absent.java:60)
        at io.digdag.spi.SecretProvider.getSecret(SecretProvider.java:20)
        at io.digdag.standards.operator.gcp.GcpCredentialProvider.credential(GcpCredentialProvider.java:28)
        at io.digdag.standards.operator.gcp.BaseGcpOperator.runTask(BaseGcpOperator.java:23)
        at io.digdag.util.BaseOperator.run(BaseOperator.java:35)
        at io.digdag.core.agent.OperatorManager.callExecutor(OperatorManager.java:315)
        at io.digdag.cli.Run$OperatorManagerWithSkip.callExecutor(Run.java:705)
        at io.digdag.core.agent.OperatorManager.runWithWorkspace(OperatorManager.java:257)
        at io.digdag.core.agent.OperatorManager.lambda$runWithHeartbeat$2(OperatorManager.java:137)
        at io.digdag.core.agent.LocalWorkspaceManager.withExtractedArchive(LocalWorkspaceManager.java:25)
        at io.digdag.core.agent.OperatorManager.runWithHeartbeat(OperatorManager.java:135)
        at io.digdag.core.agent.OperatorManager.run(OperatorManager.java:119)
        at io.digdag.cli.Run$OperatorManagerWithSkip.run(Run.java:687)
        at io.digdag.core.agent.MultiThreadAgent.lambda$null$0(MultiThreadAgent.java:127)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
2020-02-19 06:56:19 +0000 [WARN] (0016@[0:default]+auto-test^failure-alert): Skipped
error: 
  * +auto-test+step1:
    Secret not found for key: 'gcp.credential' (secret not found)
Task state is saved at /home/wvp360gqanukcqhg/test/.digdag/status/20200219T000000+0000 directory.
  * Use --session <daily | hourly | "yyyy-MM-dd[ HH:mm:ss]"> to not reuse the last session time.
  * Use --rerun, --start +NAME, or --goal +NAME argument to rerun skipped tasks.

こちらの「Secret not found for key: 'gcp.credential'」の対処方法についてご教授ください。