exec.Command does a lot of helpful things, but it currently lacks a standard API call for obtaining a process’s exit status. When troubleshooting failing processes, this value often provides important details, and Go should be able to provide this to the programmer.
As tux21b points out, there is a way to hack at this value for Linux processes, but it relies on an internal API call likely to break on different platforms. https://stackoverflow.com/questions/10385551/get-exit-code-go
What we really want is a standard, cross-platform API call for this.