gogetdoc is extremly slow on code that is using cgo

[segevfiner]

gogetdoc seems to invoke cgo, which invokes the native compiler, which can be quite slow. It does this for every invocation, with no caching, even if there were no changes in the cgo code. This ends up making gogetdoc so slow that it is unusable when you have such a package in your dependency graph.

Steps to reproduce

You need to have ImageMagick available. (See https://github.com/gographics/imagick)

1. Save the following as main.go in a new go package directory:

package main

import "gopkg.in/gographics/imagick.v2/imagick"

func main() {
	imagick.Initialize()
}

2. dep init.
3. gogetdoc -pos main.go:#87.

Related

microsoft/vscode-go#667 microsoft/vscode-go#1025

cc @ramya-rao-a

[zmb3]

Thanks for the repro - I will take a look.
gogetdoc doesn't actually support cgo but it's possible that go/packages is doing something related.

[segevfiner]

Thanks for the repro - I will take a look.
gogetdoc doesn't actually support cgo but it's possible that go/packages is doing something related.

It's probably go list -compiled used internally by go/packages. golang/tools/go/packages/golist.go#L630.