At this time there isn't. Go is a young language, and as such does not have a lot of niche libraries. You'll likely need to write your own.
All the information about the protocol is found here. From what I can gather 1.x versions are based on XML (RPC?) and uses HTTP as a transport. Version 2.x uses SOAP 1.2, which is also XML over an HTTP transport.
Unfortunately there isn't any SOAP libraries for Go either, so either way you'll need to use the net/http
and encoding/xml
packages. You'll have to make the SOAP calls reading/writing the SOAP envelopes manually.
See this answer for working with SOAP in Go.