It was announced in November 2009, but its 1.0 version was released in March 2012.
It's originally designed by Robert Griesemer, Rob Pike and Ken Thompson. They were Google engineers and Go was an experiment.
They wanted to make programming language:
that doesn't require IDE but with support for them,
that supports networking and multitasking,
that is productive and readable, without excessive boilerplate (like Ruby or Python has),
that is statically typed and scalable to large systems (ex. Java or C++).
Now Golang is used in some of Google production systems, but it's well-recognized language on whole Earth.