add a YAML definition for VSTS CI/CD

https://docs.microsoft.com/en-us/vsts/pipelines/build/yaml?view=vsts

People would be able to learn from this to build their own Go pipelines for VST.

Read the linked VSTS YAML pipeline documentation first, then inspect the repository for existing build or pipeline definitions and Go project conventions. Add a VSTS CI/CD YAML definition that demonstrates building the Go samples, and verify that the resulting pipeline configuration is valid and suitable for readers to adapt.

Written by the indexing model from the issue text.