Migrate to Go 1.16 and enable fast shutdown

Changelog for 0.5.0:

• PR #61 Allow for shorter graceful shutdown by @alexellis

Commits
c646a79 Upgrade to of-watchdog 0.9.0 by @alexellis
2931d51 Update to Alpine 1.14 by @alexellis
5f0e44b Move to Go 1.16 images by @alexellis
a693532 Add a maximum timeout for shutting down by @alexellis
b77a0ec Allow for shorter graceful shutdown by @alexellis
b29fec5 Update info message to match version by @alexellis

Changes: 0.4.0...0.5.0

Generated by Derek