update to go modules

[mcristina422]

No description provided.

[coveralls]

Coverage remained the same at 21.833% when pulling 37601a4 on mcristina422:go113 into 929d044 on grafana-tools:master.

[grafov]

@mcristina422 thank for your contribution.

• dashboard-unmarshal_test.go was fixed earlier in a separate PR it is better to remove it from this PR for clarity.
• I think we could use go modules but keep vendor directory with the packages yet — it is the safest way. If you could use modules you can build with them. Those who still use vendor libs could build without modules support. Go till 1.14 still uses GO111MODULE=auto so the build with modules is not a default way yet. cmd/go: default to GO111MODULE=auto (with changes) for Go 1.13 golang/go#31857 So I'll prefer to wait for future Go versions before totally remove vendored packages.

[mcristina422]

Sure, I can add back the vendor folder. But in go1.13 auto means go modules are on by default. https://golang.org/doc/go1.13#modules

The GO111MODULE environment variable continues to default to auto, but the auto setting now activates the module-aware mode of the go command whenever the current working directory contains, or is below a directory containing, a go.mod file — even if the current directory is within GOPATH/src.

[grafov]

@mcristina422 thank for the clarification. Really modules are on by default now. Ok, let migrate with small steps. Accept changes, thank you for this contribution!