Preview: Azure SDK for Go 12.0.0

Preview version 12.0.0-beta of the [Azure SDK for Go](https://github.com/Azure/azure-sdk-for-go) is [now available](https://github.com/Azure/azure-sdk-for-go/releases/tag/v12.0.0-beta) to help you use Azure services from Go applications. To get it, run `go get -u github.com/Azure/azure-sdk-for-go/...`, or use our newly-introduced support for [dep](https://github.com/golang/dep) and add the following lines to your Gopkg.toml: `[[constraint]] name = "github.com/Azure/azure-sdk-for-go" version = "12.0.0-beta"` Changes in this version include: * Long-running (asynchronous) operations now return a future-like construct that can be used to poll for operation completion. Previously, such operations returned channels and polling was handled internally by the library. * Support for API versions and profiles added. Use the `services/...` or `profiles/...` paths in import statements to choose specific versions and avoid unexpected breaking changes. See [our wiki](https://github.com/Azure/azure-sdk-for-go/wiki/roadmap#supporting-multiple-api-versions) for more info. * Support for [context](https://golang.org/pkg/context/) added. Library methods now all expect a Context struct as their first parameter. * Support for [dep](https://github.com/golang/dep) added and for [glide](https://github.com/Masterminds/glide) removed. * API for iterating over pageable results simplified. * New services added: * Azure Cosmos DB via MongoDB API * Azure Kubernetes Service (AKS) * Microsoft Cognitive Services: Custom Search, Entity Search, Image Search, News Search, Video Search, Web Search, and Spell Check For more details, see the [change log](https://github.com/Azure/azure-sdk-for-go/blob/master/CHANGELOG.md). Please open issues and requests in [our GitHub tracker](https://github.com/Azure/azure-sdk-for-go/issues). Thank you! * Azure Resource Manager * Azure Cosmos DB * Azure Kubernetes Service (AKS) * Azure Cognitive Services * Management * SDK and Tools * Services * [ Azure Resource Manager](https://azure.microsoft.com/en-gb/get-started/azure-portal/resource-manager/) * [ Azure Cognitive Services](https://azure.microsoft.com/en-gb/products/cognitive-services/) * [ Azure Cosmos DB](https://azure.microsoft.com/en-gb/products/cosmos-db/)