[ANNOUNCE] Apache Calcite Avatica Go 4.0.0 released

[Francis Chuang <fr...@apache.org>]

The Apache Calcite team is pleased to announce the release of Apache 
Calcite Avatica Go 4.0.0.

Avatica is a framework for building database drivers. Avatica
defines a wire API and serialization mechanism for clients to
communicate with a server as a proxy to a database. The reference
Avatica client and server are implemented in Java and communicate
over HTTP. Avatica is a sub-project of Apache Calcite.

The Avatica Go client is a Go database/sql driver that enables Go
programs to communicate with the Avatica server.

Apache Calcite Avatica Go 4.0.0 is a major release of the Avatica Go 
client. Due to this, consumers of the package will need to update their 
import paths to "github.com/apache/calcite-avatica-go/v4".

This release also features a breaking change for Apache Phoenix 
(CALCITE-2763): In Apache Phoenix, null and empty strings are 
equivalent. For some background on why this is the case, see 
PHOENIX-947. In version 3 of Avatica-Go and below, null and empty 
strings are returned as an empty string ("") to the client. This 
prevented database/sql’s built in NullString type from working 
correctly. From 4.0.0 onwards, null and empty strings will be returned 
as a nil. This allows the usage of the sql.NullString type.

For this release, both dep and Go modules are supported for package 
management. As Go modules will be turned on by default in Go 1.13.0 
(estimated to be released in September/October 2019), it is highly 
recommended that users of this package start migrating to using Go 
modules to ease the transition.

This release includes updated dependencies, testing against more
targets and an updated script to automate more of the release process 
using docker as described in the release notes:

   https://calcite.apache.org/avatica/docs/go_history.html#v4-0-0

The release is available here:

   https://calcite.apache.org/avatica/downloads/avatica-go.html

We welcome your help and feedback. For more information on how to
report problems, and to get involved, visit the project website at

   https://calcite.apache.org/avatica

or the Apache Calcite project website:

   https://calcite.apache.org/

Francis Chuang, on behalf of the Apache Calcite Team