.build();

// Connect 'em all together. Certificates are exchanged in the handshake.
Call call = client.newCall(new Request.Builder()
    .url(server.url("/"))
    .build());
Response response = call.execute();
System.out.println(response.handshake().peerPrincipal());
RecordedRequest recordedRequest = server.takeRequest();

        // Do something with payload
        return []byte("response"), nil
    }

    err := manager.RegisterSingleHandler(grid.HandlerDiskInfo, handler)
```

Sample call:
```go
    // Get a connection to the remote host
    conn := manager.Connection(host)
	
    payload := []byte("request")
    response, err := conn.SingleRequest(ctx, grid.HandlerDiskInfo, payload)
```

        all scripts can use them.
    -   `utilities/setup_docker.sh` creates a container called `tf` with all
        `TFCI_` variables shared to it.
3.  Top-level scripts (`wheel.sh`, etc.) reference `env` variables and call
    `utilities/` scripts.
    -   The `tfrun` function makes a command run correctly in Docker if Docker