Function override

Question

I found something interesting in Go. Let's say I have my package name is mypkg, inside mypkg, I have two functions:

package mypkg
func MyFunc0(){
    //...
}
var MyFunc1 = func(){
    //...
}

Now in my main package, it is possible to override MyFunc1, like this:

mypkg.MyFunc1 = func(){
   // new logic
}

However, it is not possible to override MyFunc0 the same way. So now a question is raised. What are the differences between the two ways of declaring a function? Is this behavior difference intended?

Answer 1

MyFunc0 is a function declaration (https://golang.org/ref/spec#Function_declarations)

MyFunc1 is not a function declaration. It is a variable (https://golang.org/ref/spec#Variable_declarations) of type func (see https://golang.org/ref/spec#Function_types, https://golang.org/ref/spec#Function_literals). It has an initial value, but can be changed to hold a different value/function (as long as function signatures match).