After i have written out a function in some package, it's possible to display it's documentation via
ctrl+dot,ctrl+h
Is it possible to view the documentation for each method in the code completion popup, without actually writing the statement out?
No, it's not possible. Also, you're better off opening an issue on the issue tracker https://github.com/DisposaBoy/GoSublime/issues/new . In addition to emailing me, it's fastest way to get in contact with me.