Many of the Go core contributors and well known to hold that frameworks present an unhealthy inversion of control compared to libraries. The standard library reflects this, for example as "net/http" is very much a library and works very different from applications using IIS or Apache. Many of the earliest gophers hold this position as well. I have been writing Go professionally since before Go 1.0 and I think saying "frameworks are NOT frowned upon in Go" is very much out of touch with the longest standing members of the Go community. I personally think there are cases for frameworks, but that they are few and far between.
In the case of net/http, I think it really turned out that simply integrating with http.Handler has so many more benefits than wrapping net/http with your own interfaces. Even Jeremy Saenz realized that and released Negroni after developing Martini.
Further reading for those interested:
http://www.programcreek.com/2011/09/what-is-the-difference-b...
http://tom.lokhorst.eu/2010/09/why-libraries-are-better-than...