Construction reads the file immediately. Calls check its modification time and size at
most once per second and reread when either changes. Surrounding whitespace is ignored.
An empty or unreadable file fails calls until a later check succeeds; no stale token is sent.
Reads a bearer token from a rotating file.
Construction reads the file immediately. Calls check its modification time and size at most once per second and reread when either changes. Surrounding whitespace is ignored. An empty or unreadable file fails calls until a later check succeeds; no stale token is sent.
Example