aws amplify CognitoUserSession for flutter

W/CognitoUserSession(32227): CognitoUserSession is not valid because idToken is null.

D/AWSMobileClient(32227): Sending password.

D/AWSMobileClient(32227): Using USER_SRP_AUTH for flow type.

D/AWSMobileClient(32227): _federatedSignIn: Putting provider and token in store

D/AWSMobileClient(32227): Inspecting user state details

D/AWSMobileClient(32227): hasFederatedToken: false provider: cognito-idp.us-east-2.amazonaws.com/us-east-2_DxbCXbeql

D/AWSMobileClient(32227): Inspecting user state details

D/AWSMobileClient(32227): hasFederatedToken: true provider: cognito-idp.us-east-2.amazonaws.com/us-east-2_DxbCXbeql

D/AWSMobileClient(32227): waitForSignIn: userState:SIGNED_IN

D/AWSMobileClient(32227): getCredentials: Validated user is signed-in

I am using flutter version aws amplify service on other aws iam account that is company account for developing Android app. This error occur only when using API ("Amplify.Auth.fetchUserAttributes()") after signing out and signing-in. I check that after signing in, go to home page and here call this api(I used auth_service flow you are providing on document or tutorial). But after app restart, this api works well. Only after signing out and signing-in, this API does not works. I checked userattribute in cognito service and attribute values is normal.