Fix GOROOT mismatch issues

[jonjohnsonjr]

Print a warning if GOROOT is unset and ko's default build context
differs from $(go env GOROOT) and use the result of $(go env GOROOT).

Fixes #106

[jonjohnsonjr]

I'm open to opinions here about warning or not warning or whatever, let me know how you feel about spamming stderr.

I worry that just inferring this automatically might break things that worked before without any kind of warning.

[codecov-io]

Codecov Report

Merging #303 (fd44e27) into master (3c21033) will decrease coverage by 0.03%.
The diff coverage is 38.46%.

@@            Coverage Diff             @@
##           master     #303      +/-   ##
==========================================
- Coverage   38.10%   38.07%   -0.04%     
==========================================
  Files          33       33              
  Lines        1501     1513      +12     
==========================================
+ Hits          572      576       +4     
- Misses        839      844       +5     
- Partials       90       93       +3     

Impacted Files	Coverage Δ
pkg/build/gobuild.go	59.71% <38.46%> (-0.96%)	⬇️

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[jonjohnsonjr]

Here I have modified my ko binary to have the wrong embedded GOROOT, as a demonstration of this warning in action:

$ sed -i '0,/go-1.15.5/s//jasonhall/' $(which ko)
$ ko publish .
2021/01/21 10:12:19 NOTICE!
-----------------------------------------------------------------
ko and go have mismatched GOROOT:
    go/build.Default.GOROOT = "/nix/store/1drmsvcyf0mlzhs3yzwblrwhv4hvqkkx-jasonhall/share/go"
    $(go env GOROOT) = "/nix/store/1drmsvcyf0mlzhs3yzwblrwhv4hvqkkx-go-1.15.5/share/go"

Inferring GOROOT="/nix/store/1drmsvcyf0mlzhs3yzwblrwhv4hvqkkx-go-1.15.5/share/go"

Run this to remove this warning:
    export GOROOT=$(go env GOROOT)

For more information see:
    https://github.com/google/ko/issues/106
-----------------------------------------------------------------
2021/01/21 10:12:20 Using base gcr.io/distroless/static:nonroot for github.com/google/ko
2021/01/21 10:12:21 Building github.com/google/ko for linux/amd64
2021/01/21 10:12:24 Publishing gcr.io/jonjohnson-test/ko/ko-98b8c7facdad74510a7cae0cd368eb4e:latest
2021/01/21 10:12:24 existing blob: sha256:72164b581b02b1eb297b403bcc8fc1bfa245cb52e103a3a525a0835a58ff58e2
2021/01/21 10:12:24 existing blob: sha256:d9662fda187c24492976489da64d81b5a6f034440d15c89c461cd8bb357f697d
2021/01/21 10:12:24 existing blob: sha256:5749e56bea7178768b00aac0bf087558fccd5b8e0c807610618be7568459f359
2021/01/21 10:12:24 existing blob: sha256:7d05b95b5288b7f76d3f2c5531254685d54c0c28867cb6365e96cd5774c130d6
2021/01/21 10:12:25 gcr.io/jonjohnson-test/ko/ko-98b8c7facdad74510a7cae0cd368eb4e:latest: digest: sha256:5496539d4d4eb8b0939cf8528fa8599f688e50c21d385d7f81de90e6c5f78a0a size: 750
2021/01/21 10:12:25 Published gcr.io/jonjohnson-test/ko/ko-98b8c7facdad74510a7cae0cd368eb4e@sha256:5496539d4d4eb8b0939cf8528fa8599f688e50c21d385d7f81de90e6c5f78a0a
gcr.io/jonjohnson-test/ko/ko-98b8c7facdad74510a7cae0cd368eb4e@sha256:5496539d4d4eb8b0939cf8528fa8599f688e50c21d385d7f81de90e6c5f78a0a

[jonjohnsonjr]

docker: Error response from daemon: Get https://registry-1.docker.io/v2/library/registry/manifests/2: received unexpected HTTP status: 502 Bad Gateway.

Fantastic.

[vdemeester]

Thanks for this @jonjohnsonjr 😻

[benmoss]

I'm seeing this error now and do not understand it

foo | starting build (using ko): ./cmd/kbld
foo | 2021/02/03 15:54:53 NOTICE!
foo | -----------------------------------------------------------------
foo | ko and go have mismatched GOROOT:
foo |     go/build.Default.GOROOT = "go"
foo |     $(go env GOROOT) = "/usr/local/go"
foo |
foo | Inferring GOROOT="/usr/local/go"
foo |
foo | Run this to remove this warning:
foo |     export GOROOT=$(go env GOROOT)
foo |
foo | For more information see:
foo |     https://github.com/google/ko/issues/106
foo | -----------------------------------------------------------------

I'm using the ko binary from the GitHub releases

[vdemeester]

@benmoss it's a warning, not an error. Basically it's telling you it is inferring GOROOT to be /usr/local/go. If that's not the case or if we way to remove the warning, you need to set the GOROOT env variable

[jonjohnsonjr]

Yep, I've also filed #305 as a path forward for removing this warning altogether.