The Go Programming Language Specification says:
As with selectors, a reference to a non-interface method with a value receiver using a pointer will automatically dereference that pointer: pt.Mv is equivalent to (*pt).Mv.
and:
As with method calls, a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value: t.Mp is equivalent to (&t).Mp.
So, what is non-interface method in the given context?
Interface method means the method you refer to (you call) is a call on an interface value (whose method set contains the method). Similarly, non-interface method means the method you refer to (you call) is not a call on an interface value (but on a concrete type).
For example:
var r io.Reader = os.Stdin
r.Read(nil) // Interface method: type of r is an interface (io.Reader)
var p image.Point = image.Point{}
p.String() // Non-interface method, p is a concrete type (image.Point)
To demonstrate the auto-dereferencing and address taking, see this example:
type myint int
func (m myint) ValueInt() int { return int(m) }
func (m *myint) PtrInt() int { return int(*m) }
func main() {
var m myint = myint(1)
fmt.Println(m.ValueInt()) // Normal
fmt.Println(m.PtrInt()) // (&m).PtrInt()
var p *myint = new(myint)
*p = myint(2)
fmt.Println(p.ValueInt()) // (*p).ValueInt()
fmt.Println(p.PtrInt()) // Normal
}
It outputs (try it on the Go Playground):
1
1
2
2
type T struct {}
func (t *T) f() {}
func main() {
x := T{}
x.f()
}
Above, x.f is a non-interface method.