Add go mod file

[johanbrandhorst]

Fixes #11

[johanbrandhorst]

I would also ask if we can retire 1.10.x and 1.11.x? These releases are no longer supported by the official go project, since the release of 1.13.x.

[haraldh]

Those requirements are only for the cmd. Can the go.mod file be moved there?

[coveralls]

Pull Request Test Coverage Report for Build 338

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.634%

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Totals
Change from base Build 335:	0.0%
Covered Lines:	571
Relevant Lines:	691

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 328

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.634%

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Totals
Change from base Build 327:	0.0%
Covered Lines:	1713
Relevant Lines:	2073

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💛 - Coveralls

[purpleidea]

I'd NACK. Please see: https://github.com/varlink/go/issues/11#issuecomment-536488389

[johanbrandhorst]

Those requirements are only for the cmd. Can the go.mod file be moved there?

I can move the go.mod file to ./cmd, but it can be a bit of a pain to have several modules per repository (https://github.com/golang/go/wiki/Modules#should-i-have-multiple-modules-in-a-single-repository). Are you sure?

[haraldh]

Moved the CLI tool to https://github.com/varlink/go-varlink-cmd .. so the go mod file should not be necessary

[johanbrandhorst]

As long as the generated files import github.com/varlink/go/varlink there will be a benefit to using a go.mod file. Are you planning on removing that import path?

[johanbrandhorst]

Friendly bump.