If your instance is behind an authenticating proxy that requires additional headers, they can be supplied via environment variables as follows:
SRC_HEADER_AUTHORIZATION="Bearer $(curl http://service.internal.corp)" SRC_HEADER_EXTRA=metadata src search 'foobar'
In this example, the headers authorization: Bearer my-generated-token
and extra: metadata
will be threaded to all HTTP requests to your instance. Multiple such headers can be supplied.