flutter switch to dev channel code example

Example 1: change flutter channel

flutter channel dev //for dev channel. Dev channel builds can provide early access to new features but might contain bugs. Dev channel builds are not suitable for production use.
flutter channel stable // for stable channel. Stable channel builds are tested and approved for production use.
flutter channel beta // for beta channel. Beta channel builds are preview builds for the stable channel. We recommend testing, but not releasing, your apps against beta to preview new features or test compatibility with future releases. Beta channel builds are not suitable for production use.

Example 2: flutter change to beta channel to dev

$ flutter upgrade

Flutter 0.5.1 • channel beta • https://github.com/flutter/flutter.git
Framework • revision c7ea3ca377 (9 weeks ago) • 2018-05-29 21:07:33 +0200
Engine • revision 1ed25ca7b7
Tools • Dart 2.0.0-dev.58.0.flutter-f981f09760