Linting should catch exported values without docstrings

[bobcatfish]

Expected Behavior

If someone opens a PR with exported values that don't have docstrings, linting should prompt them to add a docstring.

Actual Behavior

Nothing happens! e.g. in tektoncd/triggers#63

Steps to Reproduce the Problem

1. Add a new type to a _types.go in the triggers repo or pipeline repo, e.g.

type SomeNewThing struct {
	TriggerBinding     TriggerBindingRef  `json:"triggerBinding"`
	TriggerTemplate    TriggerTemplateRef `json:"triggerTemplate"`
	ServiceAccountName string             `json:"serviceAccountName"`
}

2. Open a PR
3. Note that the linting doesnt say anything! But actually if you opened this in an editor (e.g. vscode with the Go plugin) you'd get a warning that there should be docstrings for SomeNewThing and its attributes

Additional Info

From @vtereso :

Adding `-E golint` to our lint command (`golangci-lint run`) _should_ allow us to get [this behavior](https://github.com/golang/lint/blob/master/lint.go), but when I tried it only complained about naming stutter errors. 

(Those stutter errors are probably decent to surface as well imo! Why not :D )

[vdemeester]

@bobcatfish yeah, we should add this to the linter in the golangci configuration file. Right now, each repository has its own (see tektoncd/cli or tektoncd/triggers), we could have a default one, shared by all maybe ?

[tekton-robot]

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[tekton-robot]

@tekton-robot: Closing this issue.

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[bobcatfish]

Feels like something we should do, if we haven't already?
/remove-lifecycle stale.

[bobcatfish]

dang it

/remove-lifecycle stale

[bobcatfish]

SHOOT

[tekton-robot]

Rotten issues close after 30d of inactivity.
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/close

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[tekton-robot]

@tekton-robot: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen with a justification.
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/close

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