request: make source builds a first class approach to installation

[kortschak]

The issue template is not appropriate for this issue, so I have removed it.

In the README's installation section there is a direction to not install golangci-lint from source. Given the support for reliable builds with Go modules, this seems like an extremely odd approach.

It would be good if there were added support for source install of golang-ci lint.

Addressing the directive's points in the README:

Please, do not install golangci-lint by go get:

1. go.mod replacement directive doesn't apply. It means you will be using patched version of golangci-lint.
   There are no replace directives in that file, and if there were that would be breaking the rationale for the replace directive.
2. it's much slower than binary installation
   Surely this is up to the user to decide, being a balance between speed of install and the capacity to audit code that is running on the user's machine. Personally, I do not install from binary on my hardware, though I do allow this for travis builds.
3. its stability depends on your Go version (e.g. on this compiler Go <= 1.12 bug).
   This can be avoided by only supporting source installs for Go versions greater than 1.13. This could easily be stated as building from source is only supported for currently supported Go releases.
4. it's not guaranteed to work: e.g. we've encountered a lot of issues with Go modules hashes.
   Has this been reported anywhere?
5. it allows installation from master branch which can't be considered stable.
   If modules are used correctly, this is not the case.

[lopezator]

Hello @kortschak thank you for you report!

We ❤️ doc contributions, please feel free to open a PR linking to this issue, so we can review it.

Point 1 and Point 4 are probably outdated info (go modules and its usage here has evolved a lot lately) and might not apply anymore.

[kortschak]

I would need direction for what you consider to be acceptable documentation. What I would be suggesting here would be:

Go

Go source installations are supported for the two most recent Go releases.

GO111MODULE=on go get github.com/golangci/golangci-lint/cmd/golangci-lint

[ernado]

Looks reasonable to me, those docs are outdated.
We should also stop using vendor, because it is already a go1.14.