Proposed Changes

Similar to the frame one, there's also just one Command at a time. So it can be allocated once and updated throughout the lifetime.
This way it can be changed to a class instead of struct, and thus avoids all the complexity of the struct handling especially with the async code.

Slight performance increase as well.

Types of Changes

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Performance / simplification

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in related repositories

Further Comments

I've changed a few things along the way