Go 2 generics without syntax changes, 1 new type, 1 new builtin.

Go2GenericType.go

//A generics proposal for Go, introducing one new type (generic) and one new builtin function (typeof), no syntax changes.

//Function add takes arguments of any type.
//The return value is automatically inferred based on the arguments, can be inlined by the compiler.
//Both arguments must be the same type and addable or else a compiler error will be raised.
//It's the developer's responsibility to document which types can be passed to this function.
func add(a, b generic) generic {
    return a+b
}

add(2, 4) //returns int(6)
add("Hello ", "World") //returns string("Hello World")[
add(2, "World") //compiler error: cannot use 2, "World" (type int, string) in arguments to add
add(struct{}{}, [2]int{}) //compiler error: cannot use struct{}{}, [2]int{} (type struct{}, [2]int) in arguments to add

//New types can be created based on the generic type.
type GenericSlice generic

//Function that creates a new slice of the provided argument with length, can be inlined by the compiler.
//The return value is converted to a GenericSlice.
func MakeSliceOf(a generic, length int) GenericSlice {

	//The builtin 'typeof' function is replaced by the type of it's argument.
	return GenericSlice(make([]typeof(a), length))

}

//The get method operates on explicit GenericSlice types.
//The return value is automatically inferred based on the GenericSlice, can be inlined by the compiler.
func (g GenericSlice) Get(index int) generic {
	return g[index]
}

//The set method operates on explicit GenericSlice types.
//The value argument must be the subtype of the slice or a compiler error is raised.
func (g GenericSlice) Set(index int, value generic) {
	g[index] = value
}

var slice = MakeSliceOf(int(0), 10)
slice.Set(0, 22)
fmt.Println(slice.Get(0)) //22

slice.Set(0, "Hello World") //compiler error: cannot use "Hello World" (type string) in arguments to slice.Set

This is pretty good. Much more understandable than the current draft IMO.

Suggest you improve the formatting by adding .go extension to your gist.