x/tools/gopls: support gopls for 1.12 (current - 4)

[bvwells]

What version of Go are you using (go version)?

$ go version
go version go1.12.17 windows/amd64

Does this issue reproduce with the latest release?

No.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
set GOARCH=amd64

set GOBIN=

set GOCACHE=C:\Users\bwells\AppData\Local\go-build

set GOEXE=.exe

set GOFLAGS=

set GOHOSTARCH=amd64

set GOHOSTOS=windows

set GOOS=windows

set GOPATH=C:\Users\bwells\go

set GOPROXY=

set GORACE=

set GOROOT=c:\go

set GOTMPDIR=

set GOTOOLDIR=c:\go\pkg\tool\windows_amd64

set GCCGO=gccgo

set CC=gcc

set CXX=g++

set CGO_ENABLED=1

set CGO_CFLAGS=-g -O2

set CGO_CPPFLAGS=

set CGO_CXXFLAGS=-g -O2

set CGO_FFLAGS=-g -O2

set CGO_LDFLAGS=-g -O2

set PKG_CONFIG=pkg-config

set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\bwells\AppData\Local\Temp\go-build198506238=/tmp/go-build -gno-record-gcc-switches

What did you do?

In VSCode I updated to the latest version of gopls.

What did you expect to see?

Expected to see gopls installed correctly.

What did you see instead?

gopls failed to install due to a dependency on a package which uses a newer go language feature (errors.As) than is available in the version of go I am using (go 1.12).

gopls:
Error: Command failed: C:\Go\bin\go.exe get -v golang.org/x/tools/gopls
Fetching https://golang.org/x/tools/gopls?go-get=1
Parsing meta tags from https://golang.org/x/tools/gopls?go-get=1 (status code 200)
get "golang.org/x/tools/gopls": found meta tag get.metaImport{Prefix:"golang.org/x/tools", VCS:"git", RepoRoot:"https://go.googlesource.com/tools"} at https://golang.org/x/tools/gopls?go-get=1
get "golang.org/x/tools/gopls": verifying non-authoritative meta tag
Fetching https://golang.org/x/tools?go-get=1
Parsing meta tags from https://golang.org/x/tools?go-get=1 (status code 200)
golang.org/x/tools/internal/jsonrpc2
# golang.org/x/tools/internal/jsonrpc2
..\..\..\..\..\go\pkg\mod\golang.org\x\tools@v0.0.0-20200513154647-78b527d18275\internal\jsonrpc2\messages.go:168:5: undefined: errors.As
Fetching https://golang.org/x/tools/gopls?go-get=1
Parsing meta tags from https://golang.org/x/tools/gopls?go-get=1 (status code 200)
get "golang.org/x/tools/gopls": found meta tag get.metaImport{Prefix:"golang.org/x/tools", VCS:"git", RepoRoot:"https://go.googlesource.com/tools"} at https://golang.org/x/tools/gopls?go-get=1
get "golang.org/x/tools/gopls": verifying non-authoritative meta tag
Fetching https://golang.org/x/tools?go-get=1
Parsing meta tags from https://golang.org/x/tools?go-get=1 (status code 200)
golang.org/x/tools/internal/jsonrpc2
# golang.org/x/tools/internal/jsonrpc2
..\..\..\..\..\go\pkg\mod\golang.org\x\tools@v0.0.0-20200513154647-78b527d18275\internal\jsonrpc2\messages.go:168:5: undefined: errors.As

[gopherbot]

Thank you for filing a gopls issue! Please take a look at the Troubleshooting guide, and make sure that you have provided all of the relevant information here.

[ALTree]

From the Go release policy:

Each major Go release is supported until there are two newer major releases. For example, Go 1.5 was supported until the Go 1.7 release [...]

Since Go1.14 is out, Go1.12 is no longer a supported version; which means that gopls is allowed to break compatibility with it.

I suggest upgrading your Go version.

[bvwells]

The obvious solution is for me to upgrade to the latest version, but sadly I can't at the moment.

There is still a community on go 1.12 and it would be nice to know when this happened and what the best course of action would be other than upgrade to the latest go version.

Was advised by @heschik on slack to submit an issue.

[bvwells]

Raised an issue on the vscode-go repo for them to at least update their documentation for what versions of go it supports.

[bvwells]

Was already submitted here: golang/vscode-go#66

[stamblerre]

I've vacillated on my stance about supporting older Go versions, but I am now thinking that we should. To do this correctly, we will need to develop a gopls-specific policy like https://golang.org/doc/devel/release.html#policy, and we will need to configure TryBots with older versions of Go to run on golang.org/x/tools. I filed #39159 to track this work, as this will be the first step.

[FiloSottile]

There is still a community on go 1.12 and it would be nice to know when this happened and what the best course of action would be other than upgrade to the latest go version.

Could you elaborate on this? Widespread use of a release version out of security support is a security concern for the ecosystem and I'd like to understand if there's something we can do to avoid it.