close method
Closes the client and cleans up any resources associated with it.
Some clients maintain a pool of network connections that will not be
disconnected until the client is closed. This may cause programs using
using the Dart SDK (dart run, dart test, dart compile, etc.) to
not terminate until the client is closed. Programs run using the Flutter
SDK can still terminate even with an active connection pool.
Once close is called, no other methods should be called. If close is called while other asynchronous methods are running, the behavior is undefined.
Implementation
@override
void close() => _http.close();