Package encoding provides a number of encodings that are missing from the standard Go encoding package.
We hope that we can contribute these to the standard Go library someday. It turns out that some of these are useful for dealing with I/O streams coming from non-UTF friendly sources.
The UTF8 Encoder is also useful for situations where valid UTF-8 might be carried in streams that contain non-valid UTF; in particular I use it for helping me cope with terminals that embed escape sequences in otherwise valid UTF-8.