Do not panic on genji version when compiled in GOPATH mode

[tdemin]

The genji version command relies on the versions of modules compiled in as debug info. Those are unavailable when compiling Genji with go get github.com/genjidb/genji/cmd/shell (in GOPATH mode). This makes genji version display a message saying the version is not available if genji has been built with go get.

Sample output:

genji on master [!?] via v1.15.2 > GO111MODULE=off go run github.com/genjidb/genji/cmd/genji version
Using z.Allocator with starting ref: 8005000000000000
version not available in GOPATH mode

[tdemin]

I was thinking of returning an additional error code with cli.NewExitError("...", 1), but this would add more visual noise (it's already 2 lines of output, and this would add the 3rd one with an exit code).

[tdemin]

Related issue: #261

[tie]

Perhaps we should suggest running go get with modules enabled? Something like

fmt.Println("version not available in GOPATH mode; use \"go get\" with Go modules enabled")

[tie]

@tdemin thanks for this change, nice catch! I’ve added a minor suggestion for the GOPATH mode message.

[tdemin]

@tie sure thing, just added a notice on using modules.

[codecov-io]

Codecov Report

Merging #262 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #262   +/-   ##
=======================================
  Coverage   61.32%   61.32%           
=======================================
  Files          68       68           
  Lines        6345     6345           
=======================================
  Hits         3891     3891           
  Misses       1938     1938           
  Partials      516      516           

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[asdine]

Thanks @tdemin !