"loadinternal: cannot find runtime/cgo" with base: core20, go.mod but no cgo in code

[Jamie Strandboge]

Following https://snapcraft.io/docs/go-plugin, with a hello-world type application using golang 1.13, go.mod, base: core20, but with no cgo, using this:

base: core20
parts:
  foo:
    plugin: go
    go-channel: 1.13/stable
    source: .
    source-type: git
    stage-packages:
    - gcc
    build-environment:
    - CGO_ENABLED: "0" # didn't help

Then building I get:
$ snapcraft
...
Pulling foo
Cloning into '/root/parts/foo/src'...
done.
Building foo
+ go mod download
+ go install -p 2 -ldflags -linkmode=external ./...
# github.com/canonical/foo/cmd/foo
loadinternal: cannot find runtime/cgo
/snap/go/5828/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
/usr/bin/ld: cannot find Scrt1.o: No such file or directory
/usr/bin/ld: cannot find crti.o: No such file or directory
collect2: error: ld returned 1 exit status

Failed to build 'foo'.

Recommended resolution:
Check the build logs and ensure the part's configuration and sources are correct.
Run the same command again with --debug to shell into the environment if you wish to introspect this failure.
[2]

I tried staging different things like build-essential and libc6-dev which gave different, but failing output always related to ld.

What did work was:

base: core20
parts:
  foo:
    plugin: go
    go-channel: 1.13/stable
    source: .
    source-type: git
    build-environment:
    - CGO_ENABLED: "0" # may not be required
    override-build: |
      go install -p 2 ./...

(note I was able to drop stage-packages too).

I wonder if it makes sense that if CGO_ENABLED=0, you drop -ldflags -linkmode=external? At the very least there seems to be a documentation opportunity.

[Chris Patterson (cjp256)]

I was not able to reproduce. Can you share a full example? I tried with https://github.com/snapcore/snapcraft/tree/master/tests/spread/plugins/v2/snaps/go-mod-hello and a modified snapcraft.yaml to mirror what you're using:

name: go-mod-hello
version: "1.0"
summary: A simple go project using go.mod
description: |
  This is a basic go snap. It just prints a hello world brought in from
  a version pinned go package using go.mod.

grade: devel
base: core20
confinement: strict

apps:
  go-mod-hello:
    command: bin/go-mod-hello

parts:
  hello:
    source: .
    plugin: go
    go-channel: 1.13/stable
    stage-packages:
      - gcc
    build-environment:
      - CGO_ENABLED: "0"

[Chris Patterson (cjp256)]

Could you also try w/o `go-channel`? core20 has go 1.13 package available. I'm curious if that makes a difference in your case.

[Jamie Strandboge (jdstrand)]

$ tar -zxvf ./lp1883265.tar.gz
$ snapcraft
...
Building foo
+ go mod download
+ go install -p 2 -ldflags -linkmode=external ./...
# somewhere/test/lp1883265/cmd
loadinternal: cannot find runtime/cgo
/snap/go/5828/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
/root/parts/foo/install/usr/bin/ld: cannot find Scrt1.o: No such file or directory
/root/parts/foo/install/usr/bin/ld: cannot find crti.o: No such file or directory
collect2: error: ld returned 1 exit status

Failed to build 'foo'.

Recommended resolution:
Check the build logs and ensure the part's configuration and sources are correct.
Run the same command again with --debug to shell into the environment if you wish to introspect this failure.
[2]
$

Removing go-channel did not make a difference.

[Sergio Schvezov (sergiusens)]

Have you tried adding gcc-multilib or libc6-dev to build-packages?

[Jamie Strandboge (jdstrand)]

Using gcc, lib6-dev or gcc-multilib in build-packages makes no difference.