Gets and sets the default value of the User-Agent header for all requests generated by this HttpClient.
The default value is Dart/<version> (dart:io).
If the userAgent is set to null, no default User-Agent header will be added to each request.
String userAgent
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dart.dev/stable/2.5.0/dart-io/HttpClient/userAgent.html