I’m using the Go SDK, ProjectBackend

import (
    ws "<http://github.com/pulumi/pulumi/sdk/v3/go/common/workspace|github.com/pulumi/pulumi/sdk/v3/go/common/workspace>"
)

proj, err := ws.LoadProject("./Pulumi.yaml"))
...
proj.Backend = &ws.ProjectBackend{
	URL: "???",
}

When I set the the backend URL to

s3://…

, that works. When I set the backend URL to empty string or don’t set it, Pulumi uses the backend currently logged in at the user level. In the specific case that I manually ran a

pulumi login

to Pulumi Cloud most recently on this machine, it works. I don’t consider this viable, since I will be executing in a variety of environments and have no control of the system Pulumi login state. When I set the backend URL to

<https://app.pulumi.com>

, I get the error

error: getting user info from <https://app.pulumi.com>: unmarshalling response object: invalid character '\u003c' looking for beginning of value\n\n

Note that I am setting

PULUMI_ACCESS_TOKEN

, I have already tested that auth is not the issue. Judging from the code in the Pulumi CLI, there isn’t simply a URL I can pass in to indicate that I want to use Pulumi Cloud.