The issue is on this file
https://github.com/golang/go/blob/master/src/go/doc/testdata/issue17788.go
goplantuml assume that a function declaration with a not null receiver has a list of names for the receiver. However, when a function is declared like this, the list if also nil. We need to immediately return when such a case is found and ignore that function since it really does not have a receiver.
The issue is on this file https://github.com/golang/go/blob/master/src/go/doc/testdata/issue17788.go goplantuml assume that a function declaration with a not null receiver has a list of names for the receiver. However, when a function is declared like this, the list if also nil. We need to immediately return when such a case is found and ignore that function since it really does not have a receiver.