Sensu-go: Investigate moving from errcheck to staticcheck

[grepory]

For more information on staticcheck:

https://staticcheck.io/docs/

It looks like they have a commercial offering too so that we could sponsor development if we really like the tool.

[dgryski]

staticcheck finds more than just missing errors.

A sample report from running it over the sensu-go codebase:

commands/asset/create_test.go:116:2: this value of asset is never used (SA4006)
commands/timeutil/time.go:81:31: calling strings.Replace with n == 0 will return no results, did you mean -1? (SA1018)
commands/timeutil/time.go:81:47: calling strings.Replace with n == 0 will return no results, did you mean -1? (SA1018)
agent.go:267:33: calling regexp.MatchString in a loop has poor performance, consider using regexp.Compile (SA6000)
agent.go:351:34: calling regexp.MatchString in a loop has poor performance, consider using regexp.Compile (SA6000)
agentd/agentd.go:89:34: do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use (SA1012)
apid/apid.go:104:34: do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use (SA1012)
dashboardd/dashboardd.go:91:34: do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use (SA1012)
keepalived/keepalived.go:320:58: argument event is overwritten before first use (SA4009)

Threre are more static checkers available for Go ( https://github.com/alecthomas/gometalinter will run a number of them.)

[echlebek]

We're using gometalinter already, but are not using staticcheck yet. It's just a matter of adding it to the linter and then fixing all the problems. :)

[echlebek]

I decided to call out to megacheck instead, and fixed a bunch of lint and removed a bunch of dead code. We still have an outstanding issue in that some packages are not lint-free and we punted on fixing them, but that can be cleaned up in another effort.

[grepory]

@echlebek Happy to mindnumbingly remove lint.

[echlebek]

Little bit of stutter in the issue because of adding megacheck to the build script's go gets and forgot CHANGELOG.md entry.