headers property
HttpHeaders headersReturns the client request headers.
The client request headers can be modified until the client request body is written to or closed. After that they become immutable.
Source
HttpHeaders get headers;
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-io/HttpClientRequest/headers.html