Serverless Framework V.4 ships an installer via NPM and automatically updates its core binary itself, rather than using NPM for version management. Removing the reliance on NPM for version management helps us move the Framework toward a distributable binary, which is easier for non Node.js users. But, we need to re-implement version management/pinning to give users back control over when to update major, minor and patch versions.

We'll do this via the frameworkVersion property within serverless.yml. It should use standard semver syntax for specifying a specific version, or a range of versions. It will not error if the version is not installed. Instead it will auto-download and use the specified version before the command is run..