headers property
The global headers this context sends, without the auth header.
Read-only, and unmodifiable whether or not any headers were supplied: writing through it throws an UnsupportedError either way. It is a copy of what the caller passed, and no two contexts hand out the same instance, so a client that reached this map could not retarget its own requests, let alone those of every other client sharing the session underneath. Build a new context with withHeaders or withAdditionalHeaders to send something different.
Implementation
Map<String, String> get headers => _headers ?? const {};