Go function project with packages fails to build with s2i builder

[jrangelramos]

Go function project with packages fails to build with s2i builder, with error:

/tmp/src/.s2i/builds/last /tmp/src ~
go: f imports
	function/hello: package function/hello is not in std (/usr/lib/golang/src/function/hello)

Sample Go function project structure (full source code https://github.com/jrangelramos/gofuncpkg):

├── func.yaml
├── go.mod
├── handle.go
└── hello
    └── hello.go

handle.go

package function

import (
	"fmt"
	"function/hello"
	"net/http"
)

func Handle(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, hello.Hello("Jeff"))
}

hello/hello.go

package hello

func Hello(name string) string {
	return "Hello " + name
}

Building the above function with s2i fails as below:

func run -b s2i --build -v
Building function image
Step 1/9 : FROM registry.access.redhat.com/ubi8/go-toolset
latest: Pulling from ubi8/go-toolset
Digest: sha256:6626052118c5fa2f8ff7dcf80508f4347a6dc0f00ed67a4674ebaed427fff82a
Status: Image is up to date for registry.access.redhat.com/ubi8/go-toolset:latest
 ---> e60e55932f56
Step 2/9 : LABEL "io.openshift.s2i.build.source-location"="/tmp/gofuncpkg"       "io.k8s.display-name"="image-registry.openshift-image-registry.svc:5000/default/gofuncpkg:latest"       "io.openshift.s2i.build.image"="registry.access.redhat.com/ubi8/go-toolset"
 ---> Running in 66b3cda8f0b4
 ---> 647c848504c2
Step 3/9 : USER root
 ---> Running in 1d9352b3b087
 ---> b9fa15fef877
Step 4/9 : COPY upload/scripts /tmp/scripts
 ---> 7c4e466dd814
Step 5/9 : COPY upload/src /tmp/src
 ---> b8f869a5d7be
Step 6/9 : RUN chown -R 1001:0 /tmp/scripts /tmp/src
 ---> Running in 29442f581e96
 ---> 581baef44613
Step 7/9 : USER 1001
 ---> Running in db76e4ab6e7e
 ---> ceceb8e18ac8
Step 8/9 : RUN /tmp/scripts/assemble
 ---> Running in 4343ca78d928
/tmp/src ~
/tmp/src/.s2i/builds/last /tmp/src ~
go: f imports
	function/hello: package function/hello is not in std (/usr/lib/golang/src/function/hello)
Error: The command '/bin/sh -c /tmp/scripts/assemble' returned a non-zero code: 1

The function can be built and run properly using pack builder

[/tmp/gofuncpkg]$ func run -b pack --build   
Building function image
Still building
Still building
Yes, still building
🙌 Function built: image-registry.openshift-image-registry.svc:5000/default/gofuncpkg:latest
Running on host port 35151
Initializing HTTP function
listening on http port 8080
^Z
[/tmp/gofuncpkg]$ http :8080
HTTP/1.1 200 OK
Content-Length: 10
Content-Type: text/plain; charset=utf-8
Date: Thu, 26 Sep 2024 13:13:47 GMT

Hello Jeff