You can generate a URL using s3 pre-sign in AWS CLI. Try the following command:
AWS s3 presign s3://mybucket/myobject
This command will generate a URL that will expire in 3600 seconds
You can also provide a custom time period for the expiration using --expires-in as shown below
$ aws s3 presign s3://test-bucket/test-file.txt --expires-in 900
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